A New Perspective on Time and Gravity

This paper presents a hypothesis regarding the existence of time fused in spacetime, assuming that time possesses the properties of both a particle and a field. This duality is referred to as the field-particle of time (FPT). The analysis shows that when the FPT moves through matter, it causes time dilation. The FPT is also a significant element that appears in relativistic kinetic energy (KE = (γ - 1) · mc2). Accelerating matter to near the speed of light requires relativistic energy approaching infinity, which corresponds to the relativistic kinetic energy. Meanwhile, the potential energy (PE = mc2) from the rest mass remains constant. Then, the mass-energy equation can be rearranged in terms of PE and KE, as shown in E = (1 + (γ - 1)) · mc2. The relativistic energy of the FPT also directly affects the gravitational attraction of matter. It transfers energy to each other through spacetime. The analysis demonstrates that the gravitational force is inversely proportional to the distance squared, following Newton’s law of gravity, and it varies with the relative velocity of matter. The relationship equation between relative time and the gravitational constant indicates that a higher intensity of the gravitational field leads to a slower reference time for matter, in accordance with the general theory of relativity. A thought experiment presents a comparison of two atomic clocks placed in different locations. The first one is placed in a room temperature, around 25°C, on the surface of the Earth, and the second one is placed in high-density areas. The analysis, considering the presence of the FPT, shows that the reference time slows down in high-density areas. Therefore, the second clock must be noticeably slower than the first one, indicating the existence of the FPT passing through both atomic clocks at different speeds.

Numerical prediction of vortex flow and thermal separation in a subsonic vortex tube

This work was aimed at gaining understanding of the physical behaviours of the flow and temperature separation process in a vortex tube. To investigate the cold mass fraction’s effect on the temperature separation, the numerical calculation was carried out using an algebraic Reynolds stress model (ASM) and the standard k-ε model. The modelling of turbulence of com-pressible, complex flows used in the simulation is discussed. Emphasis is given to the derivation of the ASM for 2D axisymmet-rical flows, particularly to the model constants in the algebraic Reynolds stress equations. The TEFESS code, based on a staggered Finite Volume approach with the standard k-ε model and first-order numerical schemes, was used to carry out all the computations. The predicted results for strongly swirling turbulent compressible flow in a vortex tube suggested that the use of the ASM leads to better agreement between the numerical results and experimental data, while the k-ε model cannot capture the stabilizing effect of the swirl.

The Effect of Nb Loading on Catalytic Properties of Ni/Ce_(0.75)Zr_(0.25)O_2 Catalyst for Methane Partial Oxidation

In this study, the effect of Nb loading on the catalytic activity of Ce0.75Zr0.25O2-supported Ni catalysts was studied for methane partial oxidation. The catalysts were characterized by BET, H2 chemisorption, XRD, TPR, TEM and tested for methane partial oxidation to syngas in the temperature range of 400-800 ℃at atmospheric pressure. The results showed that the activity of methane partial oxidation on the catalysts was apparently dependent on Nb loading. It seemed that the addition of Nb lowered the catalytic activity for methane partial oxidation and increased the extent of carbon deposition. This might be due to the strong interaction between NiO and Nb-modified support and reduction of surface oxygen reducibility.

Influence of Double-sided Delta-wing Tape Insert with Alternate-axes on Flow and Heat Transfer Characteristics in a Heat Exchanger Tube

The convective heat transfer and friction behaviors of turbulent tube flow through a straight tape with double-sided delta wings(T-W)have been studied experimentally.In the current work,the T-W formed on the tape was used as vortex generators for enhancing the heat transfer coefficient by breakdown of thermal boundary layer and by mixing of fluid flow in tubes.The T-W characteristics are(1)T-W with forward/backward-wing arrangement,(2)T-W with alternate axis(T-WA),(3)three wing-width ratios and(4)wing-pitch ratios.The experimental result reveals that for using the T-W,the increases in the mean Nusselt number(Nu)and friction factor are,respectively,up to 165%and 14.8 times of the plain tube and the maximum thermal performance factor is 1.19.It is also obvious that the T-W with forward-wing gives higher heat transfer rate than one with backward-wing around 7%. The present investigation also shows that the heat transfer rate and friction factor obtained from the T-WA is higher than that from the T-W.In addition,the flow pattern and temperature fields in the T-W tube with both backward and forward wings were also examined numerically.

Free Vibration Analysis of Functionally Graded Beams with General Elastically End Constraints by DTM

The differential transformation method (DTM) is applied to investigate free vibration of functionally graded beams supported by arbitrary boundary conditions, including various types of elastically end constraints. The material properties of functionally graded beams are assumed to obey the power law distribution. The main advantages of this method are known for its excellence in high accuracy with small computational expensiveness. The DTM also provides all natural frequencies and mode shapes without any frequency missing. Fundamental frequencies as well as their higher frequencies and mode shapes are presented. The significant aspects such as boundary conditions, values of translational and rotational spring constants and the material volume fraction index on the natural frequencies and mode shapes are discussed. For elastically end constraints, some available results of special cases for isotropic beams are used to validate the present results. The new frequency results and mode shapes of functionally graded beams resting on elastically end constraints are presented.

Temperature-Insensitive Chemical Sensor with Twin Bragg Gratings in an Optical Fibre

To reduce temperature sensitivity of the fibre Bragg grating （FBG） chemical sensor, a simple method is proposed by measuring the peak wavelength difference between an etched FBG and an un-etched one in an optical fibre. Thermal characteristics and chemical sensitivity of the sensor are experimentally investigated. The experimental results indicate that the etched FBG and the rest one have almost the same thermal response, and concentration changes of the surrounding chemical solutions can be detected by measuring the peak wavelength difference between them. The sensor has been used to measure the concentrations of propylene glycol solutions and sugar solutions, and it could detect 0.7% and 0.45% concentration changes for them with an optical spectrum analyser in resolution of 10pm.

Heat Transfer Behavior in a Square Duct with Tandem Wire Coil Element Insert

Effects of insertion of tandem wire coil elements used as turbulator on heat transfer and turbulent flow friction characteristics in a uniform heat-flux square duct are experimentally investigated in this work. The experiment is conducted for turbulent flow with the Reynolds number from 4000 to 25000. The wire coil element is inserted into the duct with a view to generating a swirl flow that assists to wash up the flow trapped in the duct corners and then increase the heat transfer rate of the test duct. Apart from the full-length coil, 1D and 2D length coil elements placed in tandem inside the duct with various free-space lengths are introduced to reduce the friction loss. The results obtained from these wire coil element inserts are also compared with those from the smooth duct. The experimental results reveal that the use of wire coil inserts for the full-length coil, 1D and 2D coil elements with a short free-space length leads to a considerable increase in heat transfer and friction loss over the smooth duct with no insert. The full-length wire coil provides higher heat transfer and friction factor than the tandem wire coil elements under the same operating conditions. Also, performance evaluation criteria to assess the real benefits in using the wire coil insert into the square duct are determined.

Heat transfer in turbulent tube flow inserted with loose-fit multi-channel twisted tapes as swirl generators

Heat transfer and flow behaviors in three-dimensional circular tubes with loose-fit multiple channel twisted tapes were numerically studied. The investigation was examined for Reynolds numbers （Re） ranging from 5000 to 15,000, by using air as testing fluid. Effects of the multiple channel number （N = 2, 3, and 4）, clearance ratio （CR = 0.0, 0.025, 0.05, and 0.075） on heat transfer enhancement and flow friction were examined. The numerical results indicate that the tubes with loose-fit multiple channel twisted tapes perform higher heat transfer rates than the plain tube. The enhanced heat transfer rate is escorted with larger pressure drop. Both heat transfer and pressure drop increase with increasing multiple channel number （N） and decreasing clearance ratio （CR）. Heat transfer augmented by the loose-fit multiple channel twisted tape with N = 4 is higher than those enhanced by the ones with N = 2 and 3 by around 9.5-17.8% and 5.8-7.8%, respectively. In addition, the loose-fit multiple channel twisted tapes with clearance ratio of 0.025, 0.05, and 0.075 give lower heat transfer rates than the one with CR = 0.0 by around 8.4%, 17.5%, and 28.8%, respectively.

Science Missions Using CubeSats

As the role of missions and experiments carried out in outer space becomes more and more essential in our understanding of many earthly problems,such as resource management,environmental problems,and disaster management,as well as space science questions,thanks to their lower cost and faster development process CubeSats can benefit humanity and therefore,young scientists and engineers have been motivated to research and develop new CubeSat missions.Not very long after their inception,CubeSats have evolved to become accepted platforms for scientific and commercial applications.The last couple of years showed that they are a feasible tool for conducting scientific experiments,not only in the Earth orbit but also in the interplanetary space.For many countries,a CubeSat mission could prompt the community and young teams around the world to build the national capacity to launch and operate national space missions.This paper presents an overview of the key scientific and engineering gateways opened up to the younger scientific community by the advent and adaptation of new technology into CubeSat missions.The role of cooperation and the opportunities for capacity-building and education are also explored.Thus,the present article also aims to provide useful recommendations to scientists,early-career researchers,engineers,students,and anyone who intends to explore the potential and opportunities offered by CubeSats and CubeSats-based missions.

Heat transfer characteristics in micro-fin tube equipped with double twisted tapes: Effect of twisted tape and micro-fin tube arrangements

An experimental study was carried out to investigate the influence of double twisted-tape inserts （DTs） in micro-fin tubes （MFs） on heat transfer, friction factor and thermal performance factor characteristics of the compound devices in the following configurations： （1） twisted tapes acted in the same direction （for co-swirl） while MF and twisted tapes acted in the same （parallel） direction （MF-CoDTs：P）, （2） twisted tapes acted in the same direction （for co-swirl） while micro-fin tube and twisted tapes acted in opposite directions （MF-CoDTs：O） and （3） twisted tapes acted in opposite directions for counter swirl （MF-CDTs）. The MF alone and the MF equipped with a single twisted tape in parallel/opposite arrangement were also considered for comparison. The experiments were conducted for the flows with the Reynolds numbers between 5 650 and 17 000, under uniform heat flux condition. The experimental results indicate that MF-CDTs induce stronger swirl/turbulence flow, resulting in higher heat transfer rate, friction factor and thermal performance factor than other combined devices. The thermal performance factors associated with the use of MF-CDTs were found to be higher than those associated with the uses of MF-CoDTs：P, MF-CoDTs：O and MF alone up to 9.3%, 6.5% and 56.4%, respectively. The empirical correlations developed using the present experimental data for the Nusselt number, friction factor and thermal performance factor are also reported.

Analysis of Turbulent Heat Transfer and Fluid Flow in Channels with Various Ribbed Internal Surfaces

This paper presents results of a numerical investigation of heat transfer and flow pattern characteristics of a channel with repeated ribs on one broad wall. Numerical computations are performed for seven ribs placed on the bottom wall of a channel for Reynolds numbers ranging from 10,000 to 30,000. The newly modified ribs (the ones with convex pointing upstream/downstream rib, wedge pointing upstream/downstream rib, concave pointing upstream/downstream rib and also concave-concave rib as well as convex-concave rib), are proposed for simulation with prospect to reduce flow separation and extend reattachment area compared to the unmodified square rib. The numerical results are reported in forms of flow structure, temperature field, turbulent kinetic energy, Nusselt number, friction factor and thermal enhancement factor. The results indicate the rib with concave-concave surfaces efficiently suppresses flow separation bubble in the corner of the rib and induces large recirculation zone over those of the others, hence giving the highest Nusselt number and friction factor. On the other hand, the one with convex-concave surface provides the lowest friction factor with moderate Nusselt number. Due to the prominent effect of its low friction factor, the rib with convex-concave surface offers the highest thermal enhancement factor of 1.19.

Morphology dependent? Elucidating the catalyst structures of Ni/Ce_(0.75)Zr_(0.25)O_(2) in the steam reforming of acetic acid

In this work,the steam reforming of acetic acid was catalyzed by Ni-based catalysts supported on ceria-zirconia of different morphological structures(nanopolyhedra,nanorods,and nanocubes).The altered shapes led to the variation in catalyst properties,such as the exposed planes,ease of Ni reduction/oxidation,and carbon removal,which affected its catalytic performance.Additionally,it was found that the exposed planes present in cubic{100}and rod structures({100}and{110})enhanced the formation of Ni^(0) and subsequently promoted the reforming reaction.Moreover,oxygen vacancies and mobility properties of{100}and{110}exposed planes can promote the oxidation reaction of carbon,resulting in a stable catalyst for the reforming of acetic acid.The results also showed that the type of depositing carbons was influenced by the support morphology.All the catalysts showed a100% acetic acid conversion with the 15Ni/NC-Ce Zr(cubic structure)catalyst exhibited the highest hydrogen yield.

Methane partial oxidation over NiO-MgO/Ce0.75Zr0.25O2 catalysts

Methane partial oxidation （MPO） is considered as an alternative method to produce hydrogen because it is an exothermic reaction to afford a suitable H2/CO ratio of 2. However, carbon deposition on a catalyst is observed as a major cause of catalyst deactivation in MPO. In order to find suitable catalysts that prevent the carbon deposition, NiO-MgO/Ce0.75Zr0.2502 （CZO） supported catalysts were prepared via the co-impregnation （C） and sequential incipient wetness impregnation （S） methods. The amount of Ni loading was fixed at 15 wt-% whereas the amount of MgO loading was varied from 5 to 15 wt-%. The results revealed that the addition of MgO shifted the light-off temperatures to higher temperatures. This is because the Ni surface was partially covered with MgO, and the strong interaction between NiO and NiMgO2 over CZO support led to the difficulty in reducing NiO to active Ni~ and thus less catalytic activity. However, among the catalysts tested, the 15Ni5Mg/CZO （S） catalyst exhibited the best catalytic stability for MPO after 18 h on stream at 750℃. Moreover, this catalyst had a better resistance to carbon deposition due to its high metallic Ni dispersion at high temperature.

Turbulent heat transfer and pressure loss in a square channel with discrete broken V-rib turbulators

Turbulent periodic flow, heat transfer, friction loss and thermal enhancement characteristics in a three-dimensional horizo- ntal square channel with broken V-ribs （B-VR） are numerically investigated. The computations are based on the finite volume method, and the SIMPLE algorithm with QUICK scheme is implemented. The B-VR were installed on both sides of a plate which was diagonally placed in a square channel to produce longitudinal vortex flows through the tested section. Effects of different open comer ratios （ d/H = 0, 0.01, 0.02, 0.03, 0.04 and 0.05） on heat transfer and pressure loss in the channel and the results of the B-VR are studied. The pitch ratio （PR = p/H） and blockage ratio （BR = p/H） of B-VRs were fixed at 1.0 and 0.15, respectively. As compared with the channel without V-rib, the one with B-VRs possessed considerably higher heat transfer and friction loss. It is observed that apart from the rise of Reynolds number, the reduction of the open comer ratios leads to an increase in the Nusselt number and friction factor due to the weaker turbulence and lower resistance to the flow. According to the computational results for B-VRs, the optimum thermal enhancement is fotmd at d/H = 0.

Integrating a Market-Based Model in Trust-Based Service Systems

The reputation-based trust mechanism is a way to assess the trustworthiness of offered services, based on the feedback obtained from their users. In the absence of appropriate safeguards, service users can still manipulate this feedback. Auction mechanisms have already addressed the problem of manipulation by market- trading participants. When auction mechanisms are applied to trust systems, their interaction with the trust systems and associated overhead need to be quantitatively evaluated. This paper proposes two distributed architectures based on centralized and hybrid computing for integrating an auction mechanism with the trust systems. The empirical evaluation demonstrates how the architectures help to discourage users from giving untruthful feedback and reduce the overhead costs of the auction mechanisms.

Laminar Periodic Flow and Heat Transfer in a Rectangular Channel with Tri-angular Wavy Baffles

This paper presents a numerical analysis of laminar periodic flow and heat transfer in a rectangular constant temperature-surfaced channel with triangular wavy baffles (TWBs).The TWBs were mounted on the opposite walls of the rectangular channel with inline arrangements.The TWBs are placed on the upper and lower walls with attack angle 45?.The numerical is performed with three dif-ferent baffle height ratios (BR=b/H=0.05 0.3) at constant pitch ratio (PR) of 1.0 for the range 100 ≤ Re ≤ 1000.The computational results are shown in the topology of flow and heat transfer.It is found that the heat transfer in the channel with the TWB is more effective than that without baffle.The in-crease in the blockage ratio,BR leads to a considerable increase in the Nusselt number and friction factor.The results indicate that at low BR,a fluid flow is significantly disturbed resulting in inefficient heat transfer.As BR increases,both heat transfer rate in terms of Nusselt number and pressure drop in terms of friction factor increase.Over the range examined,the maximum Nu/Nu0 of 7.3 and f/f0 of 126 are both found with the use of the baffles with BR=0.30 at Re=1000.In addition,the flow structure and temperature field in the channel with TWBs are also reported.