The cooling and heating load distribution of large area air-conditioned room such as “open” offices, shopping malls and waiting rooms is usually assumed to be even in air conditioning system design. However, it is n...The cooling and heating load distribution of large area air-conditioned room such as “open” offices, shopping malls and waiting rooms is usually assumed to be even in air conditioning system design. However, it is not the case in reality, and a low efficient air conditioning system results from this assumption. A simulation and analysis of the cooling load distribution of an office building in Hong Kong with TRANSYS software is provided in this paper. A typical office is divided into 13 zones for simulation, including external zone, medial zone and internal zone in the north, the south, the east and the west respectively and a central zone, instead of 4 directional zone. The result shows there is much cooling load difference between each zone, and more attention should be paid to uneven indoor cooling and heating load distribution to further guide the design.展开更多
Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome （SARS） and H1N1 pandemic. Non-phar...Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome （SARS） and H1N1 pandemic. Non-pharmaceutical approaches, including ventilation system and personal protection, are believed to have certain positive effects on the reduction of co-occupant＇s inhalation. This work then aims to numerically study the performances of mouth covering on co-occupant＇s exposure under mixing ventilation （MV）, under-floor air distribution （UFAD） and displacement ventilation （DV） system, using drift-flux model. Desk partition, as one generally employed arrangement in plan office, is also investigated under MV. The dispersion of 1, 5 and 10 grn droplet residuals are numerically calculated and CO2 is used to represent tracer gas. The results show that using mouth covering by the infected person can reduce the co-occupant＇s inhalation greatly by interrupting direct spread of the expelled droplets, and best performance can be achieved under DV since the coughed air is mainly confined in the microenvironment of the infected person. The researches under MV show that the two interventions, mouth covering and desk partition, achieve almost the sarae inhalation for fine droplets while the inhalation of the co-occupant is lower when using mouth covering for large droplets.展开更多
This study aims to develop a paraffin-based phase change material(PCM) emulsion with a low extent of supercooling for thermal energy storage(TES) systems to improve the cooling efficiency.Hexadecane-water emulsions we...This study aims to develop a paraffin-based phase change material(PCM) emulsion with a low extent of supercooling for thermal energy storage(TES) systems to improve the cooling efficiency.Hexadecane-water emulsions were prepared and characterized. Multi-wall carbon nanotubes(MWCNTs) were dispersed in the emulsion as a nucleating agent to reduce the supercooling. The MWCNTs were chemically modified with carboxyl groups to improve the dispersion of the tubular particles in the organic liquid. Thermal analyses of the emulsions by differential scanning calorimeter(DSC) indicated that the extent of supercooling was significantly reduced. The concentration of the nucleating agent for an effective supercooling suppression as found to be very low, in agreement with previous findings, and there appeared to be a minimum concentration for the supercooling reduction.展开更多
As only about 15% of the total time of people in Hong Kong was spent outdoors, it would be more valuable if the associated effectiveness and impact of the recently proposed abatement measures could be expressed in ter...As only about 15% of the total time of people in Hong Kong was spent outdoors, it would be more valuable if the associated effectiveness and impact of the recently proposed abatement measures could be expressed in terms of the improvement in the total exposure levels. This paper uses an exposure assessment model developed from the local microenvironment concentration data together with our surveyed time activity patterns to evaluate the effectiveness of the proposed air pollution abatement policy. Prior to the enforcement of abatement measures, about 2.5% of the young group and 1.2% of the adult group having their exposure levels exceeded that defined by the current 8-hour PM10 standard (180 μg/m3). With the enforcement of abatement measures, only 0.3% of the adult group would be restored to a safe level.展开更多
In view of the practical importance of the heat transfer devices in various thermal engineering fields including chemical and nuclear engineering,this study aims at developing an effective method of heat transfer enha...In view of the practical importance of the heat transfer devices in various thermal engineering fields including chemical and nuclear engineering,this study aims at developing an effective method of heat transfer enhancement by using selfrotating twisted tapes(SRTTs)and Al_(2)O_(3) nanoparticles.The effect of the selfrotating twisted tapes and Al2O3 nanoparticles on the thermal performance was comprehensively investigated in a circular pipe.The experimental results indicated the heat transfer rate was effectively improved by SRTTs in comparison of plain tube.In addition,the heat transfer multiplier with SRTTs decreased from 1.38 to 1.08 with the Reynolds number increasing from 19,322 to 64,407,while the friction factor multiplier decreased from 1.61 to 1.32.Besides,the results indicated that the employment of Al_(2)O_(3) nanoparticles and SRTTs demonstrated superior thermal performance to the single SRTTs.As Reynolds number increases from 19,322 to 64,407,the heat transfer multiplier decreased from 2.08 to 1.18 in the mass concentration of 3.0%and from 1.38 to 1.08 in mass concentration of 0.0%.Finally,the new heat transfer and friction factor correlations considering the combined effect of Al2O3 nanoparticle and SRTTs were developed within 10%deviation of experimental values.展开更多
The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was u...The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.展开更多
The expression of the Maxwell magnetic monopole was employed to correlate the space to space projection that gives rise to the Gell-Mann standard model, and space to time projection which gives the leptons;and how doe...The expression of the Maxwell magnetic monopole was employed to correlate the space to space projection that gives rise to the Gell-Mann standard model, and space to time projection which gives the leptons;and how does it correlate to the Perelman mappings from the homogeneous 5D manifold to the Lorentz 4D manifold, together with correlating the physical consequences caused by the breaking of the Diagonal Long Range Order [DLRO] of the monopoles quantum states affected by the motion of massive particles in the Lorentz 4D boundary of the 5D manifold, which leads to gravitons and the gravity field via the General Relativity covariant Riemannian 4D curvatures metric equation.展开更多
A summary of the homogeneous 5D universe model is expressed in the Dirac second-order quantized representation for the magnetic monopoles, identified in terms of the Higgs Bosons, and through systematic ordered excita...A summary of the homogeneous 5D universe model is expressed in the Dirac second-order quantized representation for the magnetic monopoles, identified in terms of the Higgs Bosons, and through systematic ordered excitations of the Higgs vacuum obtained the non-homogeneous 4D Lorentz manifolds filled with masses, corresponding to making space dimension reduction projections, and thus realization of Newtonian gravity, followed by the 3D space symmetry breaking into 2D × 1D that produces the Perelmann-entropy and Ricci-Flow mappings, resulting in the realization of Poincare spheres, represented by nucleus such as Carbon 12, all the way to stars, and matter filled discs, such as stars in galaxies and 2D carbon-based molecular structures like nitrogenous bases. Finally, the forming of RNAs and DNAs, then life forms.展开更多
The technological advances in Lithium-ion batteries have created many new applications, including electric vehicles. In this short note, we shall explain in simple terms the basic physics why and how it is possible to...The technological advances in Lithium-ion batteries have created many new applications, including electric vehicles. In this short note, we shall explain in simple terms the basic physics why and how it is possible to have high energy capacity in Lithium-ion batteries. However, heating has been a common problem and without appropriate design, they might give fire and explosion as reported.展开更多
To apply the fire modelling for the fire engineer with symbolic mathematics,the key equations of a zone model were demonstrated. There were thirteen variables with nine constraints,so only four ordinary differential e...To apply the fire modelling for the fire engineer with symbolic mathematics,the key equations of a zone model were demonstrated. There were thirteen variables with nine constraints,so only four ordinary differential equations (ODEs) were required to solve. A typical fire modelling with two-room structure was studied. Accordingly,the source terms included in the ODEs were simplified and modelled,and the fourth Runge-Kutta method was used to solve the ordinary differential equations (ODEs) with symbolic mathematics. Then a zone model could be used with symbolic mathematics. It is proposed that symbolic mathematics is possible for use by fire engineer.展开更多
The main objectives were to (1) calculate the total volatile organic compounds (TVOCs) inhalation dose, (2) analyze the proportions of human’s inhaled contaminant dose from different sources, and (3) present a newly ...The main objectives were to (1) calculate the total volatile organic compounds (TVOCs) inhalation dose, (2) analyze the proportions of human’s inhaled contaminant dose from different sources, and (3) present a newly defined ratio of relative inhalation dose level (RIDL) to assess indoor air quality (IAQ). A user defined function based on CFD (computational fluid dynamics) was developed, which integrated human motion model with TVOCs emission model in a high sidewall air supply ventilation mode. Based on simulation results of 10 cases, it is shown that the spatial concentration distribution of TVOCs is affected by human motion. TVOCs diffusion characteristic of building material is the most effective way to impact the TVOCs inhalation dose. From the RIDL index, case A-2 has the most serious IAQ problem, while case D-1 is of the best IAQ.展开更多
The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this stud...The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.展开更多
Taking public transit facilities (PTFs) is the major transport style in Hong Kong. Human exposure to indoor air pollutants may cause adverse health effects to the passengers. Exposure assessment on air pollutants is i...Taking public transit facilities (PTFs) is the major transport style in Hong Kong. Human exposure to indoor air pollutants may cause adverse health effects to the passengers. Exposure assessment on air pollutants is important for the control of human diseases caused by indoor air pollution. In this paper, the indoor PM10, CO and CO 2 levels in various PTFs, such as public bus, subway, railway and ferry in Hong Kong, were mea- sured. Combining with the time budget survey of Hong Kong population,the human exposures were calculated through Monte-Carlo simulation.展开更多
With a self-similar parameter b（At） = Hi/λi, where At is the Atwood number, Hi and λi are the a.mplluae and wavelength of bubble （i = 1） and spike （i = 2） respectively, we derive analytically the solutions to ...With a self-similar parameter b（At） = Hi/λi, where At is the Atwood number, Hi and λi are the a.mplluae and wavelength of bubble （i = 1） and spike （i = 2） respectively, we derive analytically the solutions to the buoyancy-drag equation recently proposed for dynamical evolution of Rayleigh-Taylor and Richtmyer-Meshkov mixing zone. Numerical solutions are obtained with a simple form ofb（At）--- 1/（1 ＋ At） and comparisons with recent LEM （linear electric motor） experiments are made, and an agreement is found with properly chosen initial conditions.展开更多
Side branch Helmholtz resonators (HRs) are widely used to control low frequency tonal noise in air duct system. The passive Helmholtz resonator only works effectively over a narrow frequency range around resonance fre...Side branch Helmholtz resonators (HRs) are widely used to control low frequency tonal noise in air duct system. The passive Helmholtz resonator only works effectively over a narrow frequency range around resonance frequency. Changes in the exciting frequency and temperature will decrease the noise reduction performance. Many studies have been conducted on incorporating a Helmholtz resonator with active noise control to tuning the resonance frequency of HRs. The objective of this study is to study the effect of flow on the semi active Helmholtz resonator for duct noise control. Owing to a low Mach number air flow, the discontinuity condition at the joint is analytically formulated according to the conservation of the momentum and mass of air flow. Based on the transfer function at the junction, a controller function is proposed to tune the semi-active Helmholtz resonator under flow condition.展开更多
In this paper, we briefly go over the homogeneous 5D model field theory: from the 5D space-time inception, to its quantum field solutions given in terms of Higgs vacuum, filled with magnetic monopole bose fields of al...In this paper, we briefly go over the homogeneous 5D model field theory: from the 5D space-time inception, to its quantum field solutions given in terms of Higgs vacuum, filled with magnetic monopole bose fields of all energies. Then through the space dimension reduction projections, the Gell-Mann standard model was obtained as well as a quantum to Classical connection was made via introducing Bose distribution to the monopoles to obtain the Perelman entropy and Ricci Flow mappings. This provided us a picture to the creation of Astronomical objects, from galaxies to stars and planets. This method of splitting the monopole energy into ranges is extended to show that below the basic rest mass range of the electron and Quark, it still can be applied to explaining for the creation of the chemical elements periodic table. But perhaps the most interesting is in the lowest hundreds of Hz energy range, obtained from yet another 3 fold space symmetry breaking, into 2D × 1D, producing bio nitrogenous bases composed of 3 Carbon 12 in hexagon structures, due to preservation of the 1D monopole standing waves of this low frequencies. From that by imposing gauge changes the monopole states into DNA spectra. Since such spectra states retain the DLRO, it induces formation of charge carriers periodicity in a spherical bio cell.. It was then argued that due to cell’s surface proteins, the structure must contain partial filled VB, with “p” state hole density, and empty CB, separated from VB by a positive band gap. Such band structures resemble known HTC Cuprate ceramics. Since the HTC goes through a Superconductivity transition via the simultaneous bose exciton condensation, providing a Coulomb pressure, which reduces the band gap substantially, and induces the ODLRO transition of the hole density. The same obviously applies to the bio cells. Because of the near continuous exciton levels generated, a matching to the DNA spectra then can always occur by selective choices of proteins on the cell surface. Judging from a numerical study, we did years ago on YBCO, with doping. We found with a large enough VB hole density, the exciton induced superconducting gap can easily lead to <em>T</em><em>c</em> in the room temperature range. In fact by EMF excitation can increase the exciton pressure and trigger the ODLRO transition <em>T</em><em>c</em> upward. In fact, numerical results then suggest there do exist coherent EMF spectra from three key elements: Water, Carbon and Hydrogen, together with Oxygen, as studied over the years by numerous people, starting from Schr<span style="white-space:nowrap;">ö</span>dinger to most recently Geesink.展开更多
Open kitchen designs are found in small units in tall residential buildings of Asian-Oceania regions for better space utilization. As many combustibles are stored in small residential units, fire originated in the ope...Open kitchen designs are found in small units in tall residential buildings of Asian-Oceania regions for better space utilization. As many combustibles are stored in small residential units, fire originated in the open kitchen can grow and spread fast. Consequently, flashover can occur to give a big fire and result in severe casualties and property damage. Nonlinear dynamics can be applied to predict critical heat release rate to flashover in the unit with an open kitchen and will be illustrated in this paper. Based on a two-zone model, temperature of the hot smoke layer was taken as the system state variable. An evolution equation was developed with selective control parameters. Onsetting of flashover using a nonlinear dynamical system was demonstrated in the example residential units. Effects of the floor dimensions, the radiation feedback coefficient and thermal properties of wall material on the onset of flashover were then examined and analyzed. The developed nonlinear dynamical model for studying the onset of flashover gives a better understanding of the various control parameters.展开更多
In this note we give a geometrical presentation to the 4D Riemannian curvature as it relates to the Newtonian gravity in the 4D Lorentz manifold. The compacting of the proper time as is necessary for the unification w...In this note we give a geometrical presentation to the 4D Riemannian curvature as it relates to the Newtonian gravity in the 4D Lorentz manifold. The compacting of the proper time as is necessary for the unification with the Maxwell electrodynamics, as given by Einstein and Kaluza-Klein, should the universe be only of 4D space-time, led to the concept of gravitational field singularity sinks known as black holes, that would not be acceptable under a 5D homogeneous manifold through which the 4D Lorentz manifold evolved by application of the Perelman-Ricci Flow entropy mapping, which is consistent with both Maxwell suggested magnetic monopole, the quantum Higgs vacuum theory and the Gell-Mann standard model for hadrons.展开更多
Accurate building energy prediction is vital to develop optimal control strategies to enhance building energy efficiency and energy flexibility.In recent years,the data-driven approach based on machine learning algori...Accurate building energy prediction is vital to develop optimal control strategies to enhance building energy efficiency and energy flexibility.In recent years,the data-driven approach based on machine learning algorithms has been widely adopted for building energy prediction due to the availability of massive data in building automation systems(BASs),which automatically collect and store real-time building operational data.For new buildings and most existing buildings without installing advanced BASs,there is a lack of sufficient data to train data-driven predictive models.Transfer learning is a promising method to develop accurate and reliable data-driven building energy prediction models with limited training data by taking advantage of the rich data/knowledge obtained from other buildings.Few studies focused on the influences of source building datasets,pre-training data volume,and training data volume on the performance of the transfer learning method.The present study aims to develop a transfer learning-based ANN model for one-hour ahead building energy prediction to fill this research gap.Around 400 non-residential buildings’data from the open-source Building Genome Project are used to test the proposed method.Extensive analysis demonstrates that transfer learning can effectively improve the accuracy of BPNN-based building energy models for information-poor buildings with very limited training data.The most influential building features which influence the effectiveness of transfer learning are found to be building usage and industry.The research outcomes can provide guidance for implementation of transfer learning,especially in selecting appropriate source buildings and datasets for developing accurate building energy prediction models.展开更多
Occupant behavior is an important factor affecting building energy consumption.Many studies have been conducted recently to model occupant behavior and analyze its impact on building energy use.However,to achieve a re...Occupant behavior is an important factor affecting building energy consumption.Many studies have been conducted recently to model occupant behavior and analyze its impact on building energy use.However,to achieve a reduction of energy consumption in buildings,the coordination between occupant behavior and energy-efficient technologies are essential to be considered simultaneously rather than separately considering the development of technologies and the analysis of occupant behavior.It is important to utilize energy-efficient technologies to guide the occupants to avoid unnecessary energy uses.This study,therefore,proposes a new concept,“technology-guided occupant behavior”to coordinate occupant behavior with energy-efficient technologies for building energy controls.The occupants are involved into the control loop of central air-conditioning systems by actively responding to their cooling needs.On-site tests are conducted in a Hong Kong campus building to analyze the performance of“technology-guided occupant behavior”on building energy use.According to the measured data,the occupant behavior guided by the technology could achieve“cooling on demand”principle and hence reduce the energy consumption of central air-conditioning system in the test building about 23.5%,which accounts for about 7.8%of total building electricity use.展开更多
文摘The cooling and heating load distribution of large area air-conditioned room such as “open” offices, shopping malls and waiting rooms is usually assumed to be even in air conditioning system design. However, it is not the case in reality, and a low efficient air conditioning system results from this assumption. A simulation and analysis of the cooling load distribution of an office building in Hong Kong with TRANSYS software is provided in this paper. A typical office is divided into 13 zones for simulation, including external zone, medial zone and internal zone in the north, the south, the east and the west respectively and a central zone, instead of 4 directional zone. The result shows there is much cooling load difference between each zone, and more attention should be paid to uneven indoor cooling and heating load distribution to further guide the design.
基金funded by Research Grant Committee of the Hong Kong SAR government (RGC No. PolyU5265/08E)
文摘Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome （SARS） and H1N1 pandemic. Non-pharmaceutical approaches, including ventilation system and personal protection, are believed to have certain positive effects on the reduction of co-occupant＇s inhalation. This work then aims to numerically study the performances of mouth covering on co-occupant＇s exposure under mixing ventilation （MV）, under-floor air distribution （UFAD） and displacement ventilation （DV） system, using drift-flux model. Desk partition, as one generally employed arrangement in plan office, is also investigated under MV. The dispersion of 1, 5 and 10 grn droplet residuals are numerically calculated and CO2 is used to represent tracer gas. The results show that using mouth covering by the infected person can reduce the co-occupant＇s inhalation greatly by interrupting direct spread of the expelled droplets, and best performance can be achieved under DV since the coughed air is mainly confined in the microenvironment of the infected person. The researches under MV show that the two interventions, mouth covering and desk partition, achieve almost the sarae inhalation for fine droplets while the inhalation of the co-occupant is lower when using mouth covering for large droplets.
基金Supported by the Research Grant Council of the Hong Kong SAR government(GRF PolyU 5241/11E)
文摘This study aims to develop a paraffin-based phase change material(PCM) emulsion with a low extent of supercooling for thermal energy storage(TES) systems to improve the cooling efficiency.Hexadecane-water emulsions were prepared and characterized. Multi-wall carbon nanotubes(MWCNTs) were dispersed in the emulsion as a nucleating agent to reduce the supercooling. The MWCNTs were chemically modified with carboxyl groups to improve the dispersion of the tubular particles in the organic liquid. Thermal analyses of the emulsions by differential scanning calorimeter(DSC) indicated that the extent of supercooling was significantly reduced. The concentration of the nucleating agent for an effective supercooling suppression as found to be very low, in agreement with previous findings, and there appeared to be a minimum concentration for the supercooling reduction.
文摘As only about 15% of the total time of people in Hong Kong was spent outdoors, it would be more valuable if the associated effectiveness and impact of the recently proposed abatement measures could be expressed in terms of the improvement in the total exposure levels. This paper uses an exposure assessment model developed from the local microenvironment concentration data together with our surveyed time activity patterns to evaluate the effectiveness of the proposed air pollution abatement policy. Prior to the enforcement of abatement measures, about 2.5% of the young group and 1.2% of the adult group having their exposure levels exceeded that defined by the current 8-hour PM10 standard (180 μg/m3). With the enforcement of abatement measures, only 0.3% of the adult group would be restored to a safe level.
文摘In view of the practical importance of the heat transfer devices in various thermal engineering fields including chemical and nuclear engineering,this study aims at developing an effective method of heat transfer enhancement by using selfrotating twisted tapes(SRTTs)and Al_(2)O_(3) nanoparticles.The effect of the selfrotating twisted tapes and Al2O3 nanoparticles on the thermal performance was comprehensively investigated in a circular pipe.The experimental results indicated the heat transfer rate was effectively improved by SRTTs in comparison of plain tube.In addition,the heat transfer multiplier with SRTTs decreased from 1.38 to 1.08 with the Reynolds number increasing from 19,322 to 64,407,while the friction factor multiplier decreased from 1.61 to 1.32.Besides,the results indicated that the employment of Al_(2)O_(3) nanoparticles and SRTTs demonstrated superior thermal performance to the single SRTTs.As Reynolds number increases from 19,322 to 64,407,the heat transfer multiplier decreased from 2.08 to 1.18 in the mass concentration of 3.0%and from 1.38 to 1.08 in mass concentration of 0.0%.Finally,the new heat transfer and friction factor correlations considering the combined effect of Al2O3 nanoparticle and SRTTs were developed within 10%deviation of experimental values.
文摘The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.
文摘The expression of the Maxwell magnetic monopole was employed to correlate the space to space projection that gives rise to the Gell-Mann standard model, and space to time projection which gives the leptons;and how does it correlate to the Perelman mappings from the homogeneous 5D manifold to the Lorentz 4D manifold, together with correlating the physical consequences caused by the breaking of the Diagonal Long Range Order [DLRO] of the monopoles quantum states affected by the motion of massive particles in the Lorentz 4D boundary of the 5D manifold, which leads to gravitons and the gravity field via the General Relativity covariant Riemannian 4D curvatures metric equation.
文摘A summary of the homogeneous 5D universe model is expressed in the Dirac second-order quantized representation for the magnetic monopoles, identified in terms of the Higgs Bosons, and through systematic ordered excitations of the Higgs vacuum obtained the non-homogeneous 4D Lorentz manifolds filled with masses, corresponding to making space dimension reduction projections, and thus realization of Newtonian gravity, followed by the 3D space symmetry breaking into 2D × 1D that produces the Perelmann-entropy and Ricci-Flow mappings, resulting in the realization of Poincare spheres, represented by nucleus such as Carbon 12, all the way to stars, and matter filled discs, such as stars in galaxies and 2D carbon-based molecular structures like nitrogenous bases. Finally, the forming of RNAs and DNAs, then life forms.
文摘The technological advances in Lithium-ion batteries have created many new applications, including electric vehicles. In this short note, we shall explain in simple terms the basic physics why and how it is possible to have high energy capacity in Lithium-ion batteries. However, heating has been a common problem and without appropriate design, they might give fire and explosion as reported.
基金Project(PolyU B-Q01e) supported by the Research Project "Onsetting of Internal Fire Whirls in Buildings and Associated Safet Provision"
文摘To apply the fire modelling for the fire engineer with symbolic mathematics,the key equations of a zone model were demonstrated. There were thirteen variables with nine constraints,so only four ordinary differential equations (ODEs) were required to solve. A typical fire modelling with two-room structure was studied. Accordingly,the source terms included in the ODEs were simplified and modelled,and the fourth Runge-Kutta method was used to solve the ordinary differential equations (ODEs) with symbolic mathematics. Then a zone model could be used with symbolic mathematics. It is proposed that symbolic mathematics is possible for use by fire engineer.
基金Projects(2006BAJ02A08, 2006BAJ02A05) supported by the National Science and Technology Pillar Program Project during the 11th Five-Year Plan PeriodProject(2007-209) supported by the Excellent Youth Teacher of Ministry of Education of China
文摘The main objectives were to (1) calculate the total volatile organic compounds (TVOCs) inhalation dose, (2) analyze the proportions of human’s inhaled contaminant dose from different sources, and (3) present a newly defined ratio of relative inhalation dose level (RIDL) to assess indoor air quality (IAQ). A user defined function based on CFD (computational fluid dynamics) was developed, which integrated human motion model with TVOCs emission model in a high sidewall air supply ventilation mode. Based on simulation results of 10 cases, it is shown that the spatial concentration distribution of TVOCs is affected by human motion. TVOCs diffusion characteristic of building material is the most effective way to impact the TVOCs inhalation dose. From the RIDL index, case A-2 has the most serious IAQ problem, while case D-1 is of the best IAQ.
基金Supported by Competitive Earmarked Research Grant of Hong Kong Government(CERG No.522709)
文摘The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.
文摘Taking public transit facilities (PTFs) is the major transport style in Hong Kong. Human exposure to indoor air pollutants may cause adverse health effects to the passengers. Exposure assessment on air pollutants is important for the control of human diseases caused by indoor air pollution. In this paper, the indoor PM10, CO and CO 2 levels in various PTFs, such as public bus, subway, railway and ferry in Hong Kong, were mea- sured. Combining with the time budget survey of Hong Kong population,the human exposures were calculated through Monte-Carlo simulation.
文摘With a self-similar parameter b（At） = Hi/λi, where At is the Atwood number, Hi and λi are the a.mplluae and wavelength of bubble （i = 1） and spike （i = 2） respectively, we derive analytically the solutions to the buoyancy-drag equation recently proposed for dynamical evolution of Rayleigh-Taylor and Richtmyer-Meshkov mixing zone. Numerical solutions are obtained with a simple form ofb（At）--- 1/（1 ＋ At） and comparisons with recent LEM （linear electric motor） experiments are made, and an agreement is found with properly chosen initial conditions.
文摘Side branch Helmholtz resonators (HRs) are widely used to control low frequency tonal noise in air duct system. The passive Helmholtz resonator only works effectively over a narrow frequency range around resonance frequency. Changes in the exciting frequency and temperature will decrease the noise reduction performance. Many studies have been conducted on incorporating a Helmholtz resonator with active noise control to tuning the resonance frequency of HRs. The objective of this study is to study the effect of flow on the semi active Helmholtz resonator for duct noise control. Owing to a low Mach number air flow, the discontinuity condition at the joint is analytically formulated according to the conservation of the momentum and mass of air flow. Based on the transfer function at the junction, a controller function is proposed to tune the semi-active Helmholtz resonator under flow condition.
文摘In this paper, we briefly go over the homogeneous 5D model field theory: from the 5D space-time inception, to its quantum field solutions given in terms of Higgs vacuum, filled with magnetic monopole bose fields of all energies. Then through the space dimension reduction projections, the Gell-Mann standard model was obtained as well as a quantum to Classical connection was made via introducing Bose distribution to the monopoles to obtain the Perelman entropy and Ricci Flow mappings. This provided us a picture to the creation of Astronomical objects, from galaxies to stars and planets. This method of splitting the monopole energy into ranges is extended to show that below the basic rest mass range of the electron and Quark, it still can be applied to explaining for the creation of the chemical elements periodic table. But perhaps the most interesting is in the lowest hundreds of Hz energy range, obtained from yet another 3 fold space symmetry breaking, into 2D × 1D, producing bio nitrogenous bases composed of 3 Carbon 12 in hexagon structures, due to preservation of the 1D monopole standing waves of this low frequencies. From that by imposing gauge changes the monopole states into DNA spectra. Since such spectra states retain the DLRO, it induces formation of charge carriers periodicity in a spherical bio cell.. It was then argued that due to cell’s surface proteins, the structure must contain partial filled VB, with “p” state hole density, and empty CB, separated from VB by a positive band gap. Such band structures resemble known HTC Cuprate ceramics. Since the HTC goes through a Superconductivity transition via the simultaneous bose exciton condensation, providing a Coulomb pressure, which reduces the band gap substantially, and induces the ODLRO transition of the hole density. The same obviously applies to the bio cells. Because of the near continuous exciton levels generated, a matching to the DNA spectra then can always occur by selective choices of proteins on the cell surface. Judging from a numerical study, we did years ago on YBCO, with doping. We found with a large enough VB hole density, the exciton induced superconducting gap can easily lead to <em>T</em><em>c</em> in the room temperature range. In fact by EMF excitation can increase the exciton pressure and trigger the ODLRO transition <em>T</em><em>c</em> upward. In fact, numerical results then suggest there do exist coherent EMF spectra from three key elements: Water, Carbon and Hydrogen, together with Oxygen, as studied over the years by numerous people, starting from Schr<span style="white-space:nowrap;">ö</span>dinger to most recently Geesink.
文摘Open kitchen designs are found in small units in tall residential buildings of Asian-Oceania regions for better space utilization. As many combustibles are stored in small residential units, fire originated in the open kitchen can grow and spread fast. Consequently, flashover can occur to give a big fire and result in severe casualties and property damage. Nonlinear dynamics can be applied to predict critical heat release rate to flashover in the unit with an open kitchen and will be illustrated in this paper. Based on a two-zone model, temperature of the hot smoke layer was taken as the system state variable. An evolution equation was developed with selective control parameters. Onsetting of flashover using a nonlinear dynamical system was demonstrated in the example residential units. Effects of the floor dimensions, the radiation feedback coefficient and thermal properties of wall material on the onset of flashover were then examined and analyzed. The developed nonlinear dynamical model for studying the onset of flashover gives a better understanding of the various control parameters.
文摘In this note we give a geometrical presentation to the 4D Riemannian curvature as it relates to the Newtonian gravity in the 4D Lorentz manifold. The compacting of the proper time as is necessary for the unification with the Maxwell electrodynamics, as given by Einstein and Kaluza-Klein, should the universe be only of 4D space-time, led to the concept of gravitational field singularity sinks known as black holes, that would not be acceptable under a 5D homogeneous manifold through which the 4D Lorentz manifold evolved by application of the Perelman-Ricci Flow entropy mapping, which is consistent with both Maxwell suggested magnetic monopole, the quantum Higgs vacuum theory and the Gell-Mann standard model for hadrons.
基金The authors gratefully acknowledge the support of this research by the Research Grant Council of the Hong Kong SAR(152133/19E).
文摘Accurate building energy prediction is vital to develop optimal control strategies to enhance building energy efficiency and energy flexibility.In recent years,the data-driven approach based on machine learning algorithms has been widely adopted for building energy prediction due to the availability of massive data in building automation systems(BASs),which automatically collect and store real-time building operational data.For new buildings and most existing buildings without installing advanced BASs,there is a lack of sufficient data to train data-driven predictive models.Transfer learning is a promising method to develop accurate and reliable data-driven building energy prediction models with limited training data by taking advantage of the rich data/knowledge obtained from other buildings.Few studies focused on the influences of source building datasets,pre-training data volume,and training data volume on the performance of the transfer learning method.The present study aims to develop a transfer learning-based ANN model for one-hour ahead building energy prediction to fill this research gap.Around 400 non-residential buildings’data from the open-source Building Genome Project are used to test the proposed method.Extensive analysis demonstrates that transfer learning can effectively improve the accuracy of BPNN-based building energy models for information-poor buildings with very limited training data.The most influential building features which influence the effectiveness of transfer learning are found to be building usage and industry.The research outcomes can provide guidance for implementation of transfer learning,especially in selecting appropriate source buildings and datasets for developing accurate building energy prediction models.
基金The work presented in this paper is financially supported by a strategic development special project of The Hong Kong Polytechnic University.
文摘Occupant behavior is an important factor affecting building energy consumption.Many studies have been conducted recently to model occupant behavior and analyze its impact on building energy use.However,to achieve a reduction of energy consumption in buildings,the coordination between occupant behavior and energy-efficient technologies are essential to be considered simultaneously rather than separately considering the development of technologies and the analysis of occupant behavior.It is important to utilize energy-efficient technologies to guide the occupants to avoid unnecessary energy uses.This study,therefore,proposes a new concept,“technology-guided occupant behavior”to coordinate occupant behavior with energy-efficient technologies for building energy controls.The occupants are involved into the control loop of central air-conditioning systems by actively responding to their cooling needs.On-site tests are conducted in a Hong Kong campus building to analyze the performance of“technology-guided occupant behavior”on building energy use.According to the measured data,the occupant behavior guided by the technology could achieve“cooling on demand”principle and hence reduce the energy consumption of central air-conditioning system in the test building about 23.5%,which accounts for about 7.8%of total building electricity use.
