Engineering and Technology Journal

This study investigated the thermal performance of the heat pipe and conducted on the effects of working fluids with wick and vertical position. The experiments were conducted using a copper heat pipe with ( a 20.8 ) mm inner diameter, and
the length of the evaporator, the condenser, and the adiabatic regions were 300
mm, 350 mm, and 300 mm, respectively. The working fluids selected were
water, Methanol, Ethanol, and different binary mixtures (50: 50)%, (30:70)%,
and (70:30)% mixing ratios. The filling ratio for all working fluids remained
constant with the value of 50% of the evaporator volume, and the heat input
values were 20, 30, 40, and 50 watts. The results show that the heat pipe charged
with Methanol has a thermal resistance of (0.7666oC/W) which is the lowest
value of thermal resistance. The lowest thermal resistance of using mixtures is
(0.7466℃/W) for (70% methanol: 30% ethanol). Both are achieved at 50 W heat
input. Also, the highest value of heat transfer coefficient when using water as a
working fluid is (519.1073 W/m2.oC), and for using a mixture (70% water: 30%
methanol) is (805.89 W/m2.oC). Both are achieved at 50 W heat input.

Composite sandwich structures are gaining attention due to their inherent properties, such as lightweight, low density, and high strength. The forced vibration response of these structures was studied experimentally to investigate the effects of external loads on these structures. In this work, four composite sandwich structures were manufactured using carbon fiber, glass fibers, and foam and tested on a specially designed vibration test rig by hitting the specimen with an impact hammer. The response was recorded by an accelerometer attached to the specimens. The accelerometer signal was amplified, and the input and output signals were transferred to LABVIEW via a data acquisition card and were processed in MATLAB. The impact hammer acts as an external excitation source, and the frequency response function was found for each specimen under various edge boundary conditions. Bode plots were plotted for each test, and the peak frequency and the phase difference were compared. It was found that composite sandwich specimens made of carbon fiber skins and carbon fiber honeycomb core showed a higher frequency response among all specimens (400 Hz). Furthermore, it was found that the foam core layer reduces the phase difference between the input and output signals from (360 degrees) to (180 degrees) compared with other honeycomb cores. Therefore, the procedure outlined in this research can be applied to other structures to investigate their vibration response. In addition, this work could be beneficial for the diagnosis of structure stability using a forced vibration response procedure

The printed circuit heat exchanger is one of the most recent important heat exchangers, especially in the nuclear power plant and aerospace applications, due to its very compact geometry and small print foot. This paper presents a 3D numerical investigation of the thermo-hydraulic performance of PCHE with a new non-uniform channel design configuration. The new channel design consists of two different fins and shape inserts: the diamond and biconvex shapes. The influence of two design parameters on the heat exchanger performance was studied and optimized, the longitudinal and transverse pitch length (Pl) and (Pt). Air with constant properties as the working fluid with constant heat flux at the walls envelope. The Reynolds number varied from 200 to 2000. Different Pitch lengths were used (Pl=20, 30, 40, and 50) mm and (Pt=3, 4, and 5) mm. Three performance parameters were studied the Nusselt number, friction factor, and the overall performance evaluation factor. Results show that the thermal performance enhanced with decreasing the pitch lengths, and it was shown that this enhancement was found only at high Reynolds numbers above 1400. The higher enhancement factor was with NACA 0020 airfoil fins at pt=3 mm and pl=20mm of η=2.75 at Re=2000, while the worst performance was obtained with biconvex fins. The main reason behind the enhancement is the disruption of the boundary layer and the good mixing induced in the fluid flow

Photosynthesis requires additional energy. Such energy can be obtained by building a greenhouse, which traps sunlight's heat. The primary challenge in greenhouse growing is stabilizing temperature swings. Adapting conventional heating and cooling systems can provide additional energy to the greenhouse. In the greenhouse, solar energy is a vital energy source that is directly connected to the power supply. The greenhouse control systems have been adapted and implemented to meet the demands of plant cultivation due to wireless automation, design, control, and monitoring services. This study provides an effective automation system for greenhouses. It lowers the power, leads to consumption, and allows for remote control and monitoring. They show that the control model monitors sensing data are an accurate tool for computing sensing and the self-management of output devices. It was also found that this technology has several positive attributes such as easy network management and motor controls, soil moisture, humidity, temperature, and sensor to solar panel voltage. It measures the four sensors included in the suggested design system. Each sensor measures changes in the environment inside the greenhouse. All sensors are accessible in varied ratios to run devices plugged for different operations because irrigation, refrigeration, and air conditioning always start when depletion occurs.

Conserving energy and reducing emissions has become a global consensus. However, most air conditioning systems are highly energy-consuming, affecting global warming and the ozone layer because they use chlorine and fluorine refrigerating fluids. Evaporative cooling systems are one of the most important environmentally friendly air conditioning systems with low energy consumption. However, their performance is negatively affected by the high humidity of the inlet air. One of the solutions to control the relative humidity of the inlet air is using desiccant material. In this paper, a silica gel-coated heat exchanger was designed and constructed as a dehumidifying unit. The effect of airflow rate, hot water flow rate, cold water flow rate, and regeneration temperature on the system's performance has been studied. It was found that increasing the hot water flow rate improves the removing moisture from the desiccant. However,
increasing the hot water flow rate has a negative effect on the thermal
performance of the heat exchanger. The effectiveness of the heat exchanger was
53% in the regeneration phase and 52% in the cooling phase for the outside air
temperature of 40ºC, W=20 g/kg, and an airflow rate of 0.48 m³/s. From the
results shown above, it was noticed that the system could work efficiently in hot
and high humidity climates and be used in Iraqi weather.

The purpose of this paper is to present a vibration monitoring analysis of a hydrodynamic journal bearing working with nano-additives lubricants. The vibration response is generated on bearings at various rotational speeds and dynamic load conditions. These bearings were tested experimentally by adding two types of nano additives; Bismuth (3) oxide (Bi2O3), which is considered a green, nontoxic metal, as well as a new additive, and nano Titanium dioxide (TiO2), which is moderately toxic, with SN150 base oil. The performance of additives was studied on the base oil. The comparisons between the two nano-additives Bi2O3 with (1, 2, and 4 wt.%) and TiO2 with (1 and 1.25 wt.%) were studied experimentally with the SN150 base oil. And the obtained results manifested that at different concentrations of Bi2O3 and TiO2 in the SN150 base oil for each rotational speed and dynamic load, there was a reduction in the vibration system response, where Bi2O3 has a good performance at a wide range of rotational speed and dynamic load. At the same time, TiO2 performs better at higher rotational speed and dynamic load.

This paper presents an experimental and numerical study to investigate the heat transfer enhancement in a horizontal circular tube using hybrid nanofluid (CuO, Al₂O₃/ distilled water) and fitted with twisted tape (typical twisted tape, with twist ratios (TR=9.2). Under fully developed turbulent flow and uniform heat flux conditions, the studied hybrid nanofluid concentrations are (=0.6, 1.22, and 1.8% by volume). The experimental test rig includes all the required instruments to study the heat transfer enhancement. All the tests were carried out with a Reynolds number range of 3560-8320 and uniform heat flux (13217.5 W/m². The twisted tape, manufactured from polylactic acid (PLA) by 3-dimensional printer technology, was inserted inside the tube. In this numerical study, the finite volume method (CFD) procedure was employed to pattern the forced convection turbulent flow through the tube. For hybrid nanofluid with twisted, the maximum enhancement in the maximum thermal performance factor was 2.18 for φ = 1.8%, while for a tube (water with twisted) under the same conditions, it was (2.04). A high Nusselt number was obtained with a concentration of 1.8% and an enhancement in the heat transfer of about 6.70%) than water.

Rotating machine health monitoring is critical for system safety, cost savings, and increased reliability. The need for a simple and accurate fault diagnosis method has led to the development of various monitoring techniques. They incorporate vibration, motor’s current signature, and acoustic emission signals analysis in condition monitoring. So, based on using vibration signal analysis, a test rig was built for bearing fault identification. The test rig replicates and investigates various bearing problems, such as those found in the inner and outer races. An accelerometer, type ADXL335, was interfaced to a data acquisition device (DAQ USB-6215) for collecting vibration signals under various operating circumstances. In addition, a load cell was embedded with the test rig, interfaced with a digital panel meter, and used for recording the applied load on the bearings. The time-domain signal analysis technique was used after acquiring vibration signals at various bearing health states. Then, the time-domain signal was converted to the frequency domain using the fast Fourier transform, and the result was analyzed to investigate the generated fault frequencies. Finally, the obtained frequencies were compared with the theoretical values extracted from the theoretical equations, and the method proved its effectiveness in detecting the fault generated.

The most common component of mechanical systems today is rotating machines. In these systems, vibration is caused by rotating components. As a result, to decrease the amplitude of vibrations created by rotating equipment, it’s required to understand the system's behavior. In this work, the problem of vibrations in conventional bearing systems and the effect of adding active magnetic bearings to rotating machines to reduce the amplitude of vibrations are discussed. In this paper, the vibrations in the rotary bearing system were studied theoretically and analytically using simulation programs to calculate the natural frequencies and parameters affecting the performance. In the theoretical part, the shaft of the rotating bearing was analyzed by the Jeffcott method depending on several parameters that were changed with the frequency value to observe the amplitude of the vibration in the shaft. An analytical aspect by simulation, a representative model of active magnetic bearings was built using the COMSOL 2020 program, The effect of adding these bearings on capacitance, vibration reduction, and frequency behavior was examined. SolidWorks 2018 software was used to analyze the magnetic field and its distribution in the magnetic bearing coil. The results indicate that when active magnetic bearings were introduced to the rotating bearing shafts, the vibration amplitude was reduced by approximately 60%. From this work, it can be concluded that the system becomes more stable when the active magnetic bearing is added to the rotating bearing shaft, giving it a more stable and firm nature.

Resistance Spot Welding (RSW) is one of the most important welding techniques used in the automotive industry because it is an economic process and is suitable for many materials. Many parameters affect the mechanical and microstructural properties of nugget formation and its strength, like welding current, electrode force, and welding time. Therefore, optimizing the RSW process to get the optimum welding parameters is necessary for automobile manufacturing companies. High-strength steel is widely used in the automotive industry because of its superior characteristics such as high strength-weight ratio, ductility, fatigue, and corrosion resistance. This paper presents an optimization process for RSW using the Taguchi method for high strength low alloy steel (HSLA) DOCOL 500 LA, considered a new steel grade. Two spots were used in this work. The mechanical and microstructural tests are achieved to get the maximum nugget strength, nugget diameter, different welding zones microstructures, microhardness values, and failure modes. The results showed that optimum welding parameters were welding current of 8800 Amp, welding time of 20 cycles, and electrode force of 1900 N. The failure mode for optimum conditions was a full pullout with tearing of the welded sheets because of high plastic deformation and absorbed energy. The maximum microhardness value is in the fusion zone, the heat-affected region, and finally, in the base material due to the nugget zone's rapid melting and solidification process

Due to the rising demand for treated water, the enhancement of potable water yield technologies, such as traditional solar distillers, is a pressing concern. Solar desalination is one of the easiest techniques for producing fresh water from salt water. It has several benefits, not the least. It utilizes free solar energy. Moreover, it is a simple and inexpensive technique compared to other alternatives. They are, nevertheless, relatively inefficient devices. Many studies have been done to boost the daily output of solar stills by using many active strategies to produce a large amount of evaporation and condensation compared to a basic standard type distiller. The magnetic field (MF) is one of the most important and recent techniques affecting the productivity of the solar still due to its positive impact on the water evaporation rate. The primary focus of the current study is to review the effects of magnetic field approaches on the distillate production, performance, and thermal efficiency of several types of solar distillers. Based on previous studies, the magnetic field is responsible for increasing the partial pressure difference between water and glass cover. The change occurs in the hydration shells of the saltwater, which should enhance the evaporation rate and improve the performance of solar still. Besides, the magnetic field significantly reduces the surface tension of salty water, which leads to increased evaporation. Furthermore, the intensity, direction, position, and magnet sizes of magnetic have a strong effect on the rate of water evaporation as well as the rate of heat transfer

The gas turbine-based propulsion systems were responsible for the emission of pollutants that damage the ecosphere. Commercial aviation represented a large portion of carbon emissions within the aviation industry, so this study focused on novel aircraft propulsion systems for large commercial aircraft. Electric propulsion was considered to be an alternative to conventional propulsion systems. Therefore, this report analyzed the various electric aircraft concepts within the aerospace industry to see whether they have environmental benefits. A flying wing aircraft was compared to a conventional tube-and-wing aircraft using Computational Fluid Dynamics to determine which aircraft requires more power. The lift forces acting on the conventional aircraft and flying wing at cruise speed were 269,110 N and 10681 N, while the drag forces acting on the conventional aircraft and Flying Wing Aircraft at cruise speed were 260,940 N and 7679 N, respectively. More electric aircraft approach has allowed the older power subsystems to be replaced by electrical systems within modern aircrafts such as the Boeings, airbus, etc. This has increased fuel efficiency. The result of the lift power requirement should be a boost for battery companies to develop FWA. Conclusively, the result inferred that the Flying Wing Aircraft is more aerodynamic and, therefore, would improve aircraft efficiency and emit less emission.

Determination of Temperature-Time Profile by the Lumped thermal mass analysis (LTMA) method using Tiger-Nut Juice as the impinging fluid on the cooling system was carried out. With a stationary hot steel plate on a modified run-out table for the top surface controlled the accelerated cooling process. This was evaluated with pipe diameters of 10 mm, 15 mm, 30 mm, 35 mm, and 40 mm by single jet Tiger-Nut Juice impinging fluid, impingement gaps of 115 mm, 125 mm, 135 mm, 145 mm, and 155 mm, initial surface temperatures from 450℃ – 410℃ and at sub-cooled temperatures from 150℃–110℃. The analysis reveals a faster cooling rate for both diameters at an impingement gap of 155 mm. Diameter 10mm with 1.8℃/sec average rate, for impingement gap of 115 mm, 1.8℃/sec for impingement gaps of 125 mm, 135 mm and 145 mm and 1.9℃ for 155mm. This optimal temperature-time profile of Tiger Nut Juice impingement cooling infers that a higher cooling rate is achieved using smaller pipe diameter D and higher impingement gap H. In addition, it showed evidence of less Leiden frost phenomenon; hence, extracted tiger nut juice fluid can perfectly serve as a substitute for water at smaller pipe diameters and higher impingement gaps. Also, it was inferred that it also cools at a bigger pipe diameter with a lower impingement gap.

The draught requirement of a single-furrow animal-drawn mouldboard plough implement was determined on sandy loam soils from June to July 2021 at Modibbo Adama University, Yola. The effect of speeds (0.65, 0.83, and 1.05 ms-1) and depths (8, 13, and 18 cm) upon the draught was investigated. Soil analysis, animal specification, and results of tillage experiments are reported. A pair of oxen weighing 538 kg was used as a power source. A 1 x 3 x 3 factorial experimental design was arranged in a Randomized Complete Design (RCD) for the study on a test plot of 50 m long x 25 m wide and replicated three times. The highest mean draught values of 458.43 N and the lowest mean draught values of 456.03 N were obtained at a speed and depth combination of 1.05 ms-1 and 0.183 m and 0.65 ms-1 and 0.083 m, respectively, with a unit draught of 11.07 kpa. Analysis of Variance (ANOVA) between speed and depth had a significant effect at a 1% level of probability (P≤0.01) on draught requirement. Linear regression equations showed an increase in draught with an increase in tillage depth and speed. The high coefficient of determination r2 values show that the plough is operated more economically at a mean speed of 0.83 m/s and a depth of 0.135 m. These regression equations can predict draught during the design of animal-drawn tillage implementation. Substantial energy savings can be obtained with proper animal-tillage implements combination.

Electrical energy from offshore wind turbines is an important source of clean, renewable energy production. One of the reasons for the low efficiency of wind turbines is the change in the flow angle of attack, denoted by the symbol (α), as a result of the deflection of the structure. The study aims to know the values of the maximum deflection of the proposed structure under the environmental conditions of the Arabian Gulf water area. Our research adopted a novel approach to extracting results; the characteristics of sea waves were extracted from the experimental work after fixing five sea waves, knowing the displacement of the top of the structure, and using the numerical approach in the ANSYS-Fluent program to know the average wind and wave forces. Two simulations were performed. The first included the five cases of sea wave characteristics without rotating wind turbine blades. The second was for the fifth case only with the wind turbine blades rotating at a speed of (20.5 rpm), assuming that the structure was exposed to a constant wind speed (12 m/s) for the two simulations. The study also included obtaining the maximum deflection value of the structure. Then, the equations of the theoretical approach were developed based on the Euler-Bernoulli bending moment equation, and the forces extracted from the simulations were entered into the theoretical equations to extract the maximum deflection values of the structure. Reading the experimental work resulted in the highest displacement of the top of the structure in the fifth case (0.178 m). The result of the second simulation had the highest value of the structure deflection (0.201 m). In comparison, its value came in the theoretical approach (0.160 m), which adopted the forces of the second simulation.

The present work studied the influence of pulsating flow as an active method on the thermal performance of a double-pass solar air heater with a tubular solar absorber. A ball valve has been used as a pulse generator mounted at the downstream flow of the solar air heater. The experiments were under indoor conditions with a constant heat flux of 1000 W/m2, and different air mass flow rates ranged from 0.01 to 0.03 kg/s. Moreover, the study covered three pulsation frequencies varied from 1 to 3 Hz. Based on the experimental outcomes, it can be observed that the heat transfer rate is enhanced by applying the pulsating flow, where it was found that the outlet temperature in the case of applying the pulsating flow rises by about 25.6 - 27% as compared with the steady flow case. Moreover, pulsating flow offers a higher effective thermal performance by about 15.2% at the maximum air mass flow rate compared with the steady flow. In addition, the findings pointed out that varying the pulsation frequency from 1 to 3 Hz produces an enhancement in heat transfer rate and in solar heater effective efficiency, where it was found that when changing the frequency from 1 to 3, the increment of effective efficiency ranged from 3.8 to 6.9% depending on the air mass flow value.

To save the environment and utilize the waste heat associated with exhaust gases of internal combustion engines, it is crucial to design an efficient system that can recover this heat loss and convert it into useful energy. This study is devoted to developing, through an experimental approach, a practical technical solution to minimize the waste heat of the exhaust gases and convert it into a source of power for further applications in the vehicle. Six thermoelectric generators (TEG1-1263-4.3) were attached to the exhaust pipe in an arrangement of three connected in parallel and three connected in series. The thermoelectric generators were in a square shape of size 30 mm x 30 mm, and operated at a maximum temperature of 320℃. The experiments were conducted for a vehicle speed limit between (10 km/h - 60 km/h). It has been found that at a vehicle speed of 55 km/h, the exhaust pipe surface temperature reached approximately 116℃. For six models of TEGs, the output voltage was 4.13 volts. And the system efficiency was found to vary between 3.6% -15.9%, depending on the surface temperature of the exhaust pipe, i.e., the surface temperature that is in contact with the hot side of the thermoelectric generators. Such outputs refer to the efficiency of TEGs to be used as a heat recovery system. Furthermore, the produced power can be used for feeding other applications within the vehicle, such as using a small fridge for a cooling process.

As mobile robots have become widespread in indoor environments with narrow and crowded corridors, such as institutions, the demand for mobile robots has recently increased, especially for service purposes (homes, hospitals, and nursing homes for the elderly). The most important factor of autonomous navigation is the mobile robot's awareness of its surroundings, with the robot's ability to move from one place to another smoothly and safely in terms of avoiding obstacles. In this paper, a mobile robot with multi-directional wheels was designed to work in indoor environments and narrow corridors. SLAM was used to map the environment in which the robot operates, as well as determine the robot's location within this environment based on the data of the LIDAR sensor. The robot was controlled through the ROS robot operating system. In this research, we conducted a practical experiment for the robot's movement inside a corridor and mapped this corridor by SLAM.

Convection heat transfer inside an empty triangular channel when filled with porous media heated proportionally with a constant heat flux (1300 W/m²) at the Reynolds number range (3165- 10910) with packed beds has been studied. The present work investigates porous media experimentally. The packed duct has a length (1 m) and (0.1 m) hydraulic diameter packed with porous material made from spherical glass particles of two different diameters (5 mm, and 10 mm). The value of porosity for the channel is (0.468,0.616 and), respectively. This research studies the effect of changing the Reynolds number and porosity on the enhanced heat transfer coefficient and local Nusselt number. The results indicated that using a porous structure enhanced the convection heat transfer coefficient significantly by (90.2%) and (92.1%) at porosity (0.616, 0.468), respectively, when compared with an empty duct. The results also revealed that the local Nusselt number decreased when the flow's axial position increased with increasing air velocity. The pressure on both ends of the test section increased as the air velocity rose and reduced as the size of the glass spheres increased. Therefore, the drag coefficient decreases as the modified Reynolds number increases with the diameter of glass spheres. The current research was compared with previous research, and the results were satisfactory. Correlational
relationships were reached between the Nusselt number and the Reynolds
number.

This research aims to study the effect of rectangular grooves on the lubrication mechanism in an inclined slider bearing. Reynolds' equation was used in the theory part to calculate the pressure gradient in a one-dimensional fluid film. The tilted sliding bearing compared the practical results, where the researcher manufactured and developed the device by adding pressure sensors along with the pad. These sensors will give accurate readings because they will read the pressure directly from the bottom of the pads without manometer tubes. Four pads were manufactured, one without grooves and three with rectangular grooves, varying slot widths (3, 5, 8 mm), and a depth of 2mm. This study examined various variables: sliding velocities, pad inclination values, and oil temperatures. The conclusions indicated that the flat model is significantly superior to the groove’s models. One significant finding for grooved models is that as the inclination increases, the maximum load capacity approaches the pad's center, allowing grooved models to be used in applications requiring less load and weight. The maximum load-carrying capacity of flat and grooved models was in the film ratio (K) = 2–2.5. In contrast, the load capacity of the flat model was greater than that of the groove model by percentages of 0.5%, 4.27%, and 14.66%, respectively. Moreover, the flat model's coefficient of friction is lower than the coefficient of friction of the groove models, with percentages of 0.38%, 4.63%, and 17.37%, respectively.

This study investigates the effects of Eichhornia Crassipes Biodiesel (ECB) with liquefied petroleum gas (LPG) dual-fuel on diesel engine performance and exhaust emissions characteristics. A four-stroke, single-cylinder and water-cooled diesel engine was used. The engine was operated with pure Iraqi diesel (PID) as a reference fuel, 40% ECB-60% PID, and duel fuel mode (DFM) (40% ECB-60% PID-2.4 l/min LPG). The experimental testing was carried out at 1500 rpm constant engine speed, compression ratio 18, and time injection 23° bTDC under various load conditions (25%, 50%, 75%, and 100%) full load. Using a gas analyzer, the engine emissions, including carbon dioxide (CO2), carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxides (NOx), were measured. An OPABOX smoke unit was used to determine the smoke intensity. The result manifested that the 40% ECB reduced the thermal brake efficiency (BTH) by 7% at partial load, compared with the PID. Exhaust emissions tests at full load displayed a reduction in CO2, CO, HC, and smoke by 44.4%, 70.34%, 31%, 76%, and 47%, respectively, with increasing NOx emission by 17.02% compared with the PID. The (LPG- 40% ECB) DFM at full load elucidated a reduction in CO2, CO, and smoke by (52.38%-14.28%), (81.48%- 37.5%) and (86.28 %-
41.7%), respectively, while there was an increase in HC and NOx emission by of
(15.38%-40%) and (34.2%-20.07%), respectively, compared with the PID and
40% ECB, where the BTH in DFM was higher than 40% ECB by 9.07%.
Finally, the brake-specific fuel consumption (BSFC) decreased by (10.11%-
11.2%) compared with PID and 40% biodiesel.

Metal foam is a novel material recently utilized in baffles as an alternative to solid baffles for reducing flow resistance. However, copper foam baffles have been suggested in this research to overcome this issue. So, the experimental tests were carried out in a manufactured square channel (250 mm x 250 mm) and heated uniformly at the bottom wall of the test section. Its walls are mounted copper foam baffles at a fixed porosity of 95%. Baffles were fixed alternatively on the top and bottom of the walls in staggered mode between two successive baffles (center to center) and were kept constant at 250 mm. The experimental work was done for different grades of the pore density of copper foam (10, 15, and 20 pores per inch (PPI)) with a window cut ratio of 25% and a constant heat flux of 4.4 kW/m2. Reynolds number was varied from 3.8x104 to 5.4x104. The data for conventional copper solid baffles were used to compare the effect of foam metal baffles. The obtained results manifested that relative to the solid-copper baffles, the copper foam baffles have a greatly lower friction factor, whereas the friction factor for the solid baffles and copper foam baffles (10, 15, and 20) PPI is about (460), and (20, 29, and 38) times, respectively above the smooth surface. Moreover, the results of previous work predicted the present experimental work very well.