This paper investigates theoretically the behavior of the space charge region of a silicon solar cell and its associated capacitance under the effect of an external electric field. The purpose of this work is to show ...This paper investigates theoretically the behavior of the space charge region of a silicon solar cell and its associated capacitance under the effect of an external electric field. The purpose of this work is to show that under illumination the solar cell’s space charge region width varies with both operating point and the external induced electric field and how the solar cell capacitance varies with the space charge region width. Based on a 1D modelling of the quasi-neutral p-base, the space charge region width is determined and the associated capacitance is calculated taking into account the external electric field and the junction dynamic velocity. Based on the above calculations and simulations conducted with Mathcad, we confirmed the linear dependence of the inverse capacitance with space charge region width for thin space charge region and we exhibit an exponential dependence for large space charge region.展开更多
The architecture of the Great Pyramid at Giza is based on fascinating golden mean geometry. Recently the ratio of the in-sphere volume to the pyramid volume was calculated. One yields as result <em>R</em>&...The architecture of the Great Pyramid at Giza is based on fascinating golden mean geometry. Recently the ratio of the in-sphere volume to the pyramid volume was calculated. One yields as result <em>R</em><sub><em>V</em></sub> = π <span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span> <em><em style="white-space:normal;">φ</em></em><sup>5</sup>, where <img src="Edit_83decbce-7252-44ed-a822-fef13e43fd2a.bmp" alt="" /> is the golden mean. It is important that the number <em>φ</em><sup>5</sup> is a fundamental constant of nature describing phase transition from microscopic to cosmic scale. In this contribution the relatively small volume ratio of the Great Pyramid was compared to that of selected convex polyhedral solids such as the <em>Platonic </em>solids respectively the face-rich truncated icosahedron (bucky ball) as one of <em>Archimedes</em>’ solids leading to effective filling of the polyhedron by its in-sphere and therefore the highest volume ratio of the selected examples. The smallest ratio was found for the Great Pyramid. A regression analysis delivers the highly reliable volume ratio relation <img src="Edit_79e766ce-5580-4ae0-a706-570e0f3f1bd8.bmp" alt="" />, where <em>nF</em> represents the number of polyhedron faces and b approximates the silver mean. For less-symmetrical solids with a unique axis (tetragonal pyramids) the in-sphere can be replaced by a biaxial ellipsoid of maximum volume to adjust the <em>R</em><sub><em>V</em></sub> relation more reliably.展开更多
When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric envir...When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric environment will produce a variety of adverse effects on the signal. The interference produced by these effects overlaps with each other, which will seriously affect the strength of the received signal. Therefore, how to effectively suppress the atmospheric turbulence effect in the random atmospheric turbulence channel, ensure the normal transmission of the signal in the atmospheric channel, and reduce the bit error rate of the communication system, is very necessary to improve the communication system. When processing the received signal, it is an important step to detect the transmitted signal by comparing the received signal with the threshold. In this paper, based on the atmospheric turbulence distribution model, the adaptive signal decision threshold is obtained through the estimation of high-order cumulant. Monte Carlo method is used to verify the performance of adaptive threshold detection. The simulation results show that the high-order cumulant estimation of atmospheric turbulence parameters can realize the adaptive change of the decision threshold with the channel condition. It is shown that the adaptive threshold detection can effectively restrain atmospheric turbulence, improve the performance of free space optical and improve the communication quality.展开更多
目的验证三维多回波数据联合成像(three dimensional multi-echo data imagine combination with selective water excitation,3D MEDIC WE)和三维快速自旋回波成像(three dimensional sampling perfection with application optimized ...目的验证三维多回波数据联合成像(three dimensional multi-echo data imagine combination with selective water excitation,3D MEDIC WE)和三维快速自旋回波成像(three dimensional sampling perfection with application optimized contrasts by using different flip angle evolution,3D SPACE STIR)序列在腰骶丛神经根成像中的可行性和重复性。方法将55例受试者分为腰椎无异常表现的正常对照组(20例)、单纯性腰椎间盘突出症(lumbar disc herniation,LDH)组(20例)和慢性炎性脱髓鞘性多发性神经根神经病症(chronic inflammatory demyelinating polyradiculoneuropathy,CIDP)组(15例),分别应用两种腰骶丛神经根成像,评价图像质量参数信噪比(signal to noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)和对比度(contrast ratio,CR),并验证正常对照组、CIDP组和LDH组测量神经根直径的一致性。结果两序列测得神经根直径的一致性较高(正常组r=0.95,CIDP组r=0.99,LDH组r=0.97,P<0.001),图像质量评价指标显示,3D SPACE STIR序列在SNR、CNR和CR三项指标中占优,3D MEDIC WE定性评估图像质量评分较高。两序列均能清晰显示正常腰骶丛神经根、病变所致的弥漫性形态增粗神经根以及间盘突出受挤压变形的神经根。结论3D MEDIC WE和3D SPACE STIR序列可应用于腰骶丛神经根成像,两序列对正常和异常形态、走行的神经根评估具备很高的可行性和重复性。综合考量临床图像的定性、定量评价,可择优选择恰当的序列为腰骶丛神经根成像提供影像支持。展开更多
The construction of urban green space has attracted extensive attention of researchers under the background of urban sustainable development and ecological civilization construction.The research of urban green space i...The construction of urban green space has attracted extensive attention of researchers under the background of urban sustainable development and ecological civilization construction.The research of urban green space involves ecology,geography,economics,sociology and other disciplines,among which geography has played an important role in promoting the study and practice of green space in terms of research perspectives,methods and techniques,planning and management.In this paper,the important role of urban geography in green space research is analyzed from defi nition,classifi cation to multidisciplinary background,and the research and practice progress of green space in urban geography are summarized in four aspects:characteristics and division of green space,relationship between green space and urban regional structure,service function of urban green space,and the relationship between green space and urban development.Finally,the practical achievements of green space research are illustrated from the perspective of urban geography.展开更多
BACKGROUND The introduction of modern diagnostic tools has transformed the field of maxillofacial radiology.Odontogenic infection and fascial space involvement have been evaluated with many diagnostic tools,including ...BACKGROUND The introduction of modern diagnostic tools has transformed the field of maxillofacial radiology.Odontogenic infection and fascial space involvement have been evaluated with many diagnostic tools,including ultrasonography(USG)and magnetic resonance imaging(MRI).AIM To explore USG as an alternative model to MRI in the detection of fascial space spread of odontogenic infections.METHODS Among 20 patients,50 fascial spaces were clinically diagnosed with odontogenic infection and included in this prospective study.Fascial space infection involvement was examined by USG and MRI.Results were compared for both and confirmed by microbiological testing.RESULTS Ultrasonography identified 42(84%)of 50 involved fascial spaces.Whereas MRI identified all 50(100%).USG could stage the infections from edematous change to cellulitis to complete abscess formation.CONCLUSION MRI was superior in recognizing deep fascial space infections compared to USG.However, USG is a significant addition and has a definite role in prognosticatingthe stage of infection and exact anatomic location in superficial space infections.展开更多
Hawking-Page phase transitions between the thermal anti-de Sitter vacuum and charged black holes sur・rounded by quintessence are studied in the extended phase space.The quintessence field,with the state parameter-1<...Hawking-Page phase transitions between the thermal anti-de Sitter vacuum and charged black holes sur・rounded by quintessence are studied in the extended phase space.The quintessence field,with the state parameter-1<w<-1/3,modifies the temperature and the Gibbs free energy of a black hole.The phase transition temperature Thp and the Gibbs free energy G are first analytically investigated for the special case of w=-2/3,and then,the results of numerical simulations are shown for general w.The phase transition temperature Thp increases with pressure and decreases with electric potential.In addition,Thp significantly decreases owing to the quintessence field,which generates negative pressure around the black hole.展开更多
In this article,we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology,such as small covers,quasi-toric manifolds and(real)moment-angle manifo...In this article,we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology,such as small covers,quasi-toric manifolds and(real)moment-angle manifolds;especially for the cases of small covers and quasi-toric manifolds.These kinds of orbit configuration spaces have non-free group actions,and they are all noncompact,but still built via simple convex polytopes.We obtain an explicit formula of the Euler characteristic for orbit configuration spaces of small covers and quasi-toric manifolds in terms of the h-vector of a simple convex polytope.As a by-product of our method,we also obtain a formula of the Euler characteristic for the classical configuration space,which generalizes the Félix-Thomas formula.In addition,we also study the homotopy type of such orbit configuration spaces.In particular,we determine an equivariant strong deformation retraction of the orbit configuration space of 2 distinct orbit-points in a small cover or a quasi-toric manifold,which allows to further study the algebraic topology of such an orbit configuration space by using the Mayer-Vietoris spectral sequence.展开更多
The paper belongs to the sphere of quantum physics, physics of waves and physical fields, in particular—to the gravitation. Their study provides a better understanding of the problems of natural sciences at all level...The paper belongs to the sphere of quantum physics, physics of waves and physical fields, in particular—to the gravitation. Their study provides a better understanding of the problems of natural sciences at all levels, from elementary particles, to Universe as a whole. Therefore, the solution of these problems is an urgent and important task, which to the works of many generations of scientists of the world was dedicated. However, they have not been fully resolved. In well-known works, including general relativity, determination of the wave and energy parameters of the gravitational field of the Universe and their numerical values are absent. Solutions found are limited to tensor equations of a general form, which allows their interpretation of over a wide range. Other disadvantages of famous models are: 1) the voluminous world of the Universe reduced to the planes on which space objects and other objects move, sagging planes due to their own mass;2) signs of “top” and “bottom” of the system, which are not in the real Universe, just as they are not on Earth and not in the Solar system;3) the formation of “voids” between the object and the curved space and others. Main goals of the work to identify these contradictions and find ways to resolve them are performed. The main difference and the scientific novelty of the work performed are the justification of the gravity model based on a rigorous determination of the wave and energy parameters of the gravitational field of the Universe and their numerical values. The initial parameters of this worked—is the frequency oscillation <em>ν</em><sub><em>G</em></sub> of the waves of the gravitational field (Nastasenko’s constant) found in 2011. <strong>Research Results:</strong> Knowing <em>ν</em><sub><em>G</em></sub> can find all wave parameters of the gravitational field and their numerical values. The proposed new spatial-wave model of the action of gravity is based on the wave parameters of the gravitational fields of material objects. In the framewor展开更多
文摘This paper investigates theoretically the behavior of the space charge region of a silicon solar cell and its associated capacitance under the effect of an external electric field. The purpose of this work is to show that under illumination the solar cell’s space charge region width varies with both operating point and the external induced electric field and how the solar cell capacitance varies with the space charge region width. Based on a 1D modelling of the quasi-neutral p-base, the space charge region width is determined and the associated capacitance is calculated taking into account the external electric field and the junction dynamic velocity. Based on the above calculations and simulations conducted with Mathcad, we confirmed the linear dependence of the inverse capacitance with space charge region width for thin space charge region and we exhibit an exponential dependence for large space charge region.
文摘The architecture of the Great Pyramid at Giza is based on fascinating golden mean geometry. Recently the ratio of the in-sphere volume to the pyramid volume was calculated. One yields as result <em>R</em><sub><em>V</em></sub> = π <span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span> <em><em style="white-space:normal;">φ</em></em><sup>5</sup>, where <img src="Edit_83decbce-7252-44ed-a822-fef13e43fd2a.bmp" alt="" /> is the golden mean. It is important that the number <em>φ</em><sup>5</sup> is a fundamental constant of nature describing phase transition from microscopic to cosmic scale. In this contribution the relatively small volume ratio of the Great Pyramid was compared to that of selected convex polyhedral solids such as the <em>Platonic </em>solids respectively the face-rich truncated icosahedron (bucky ball) as one of <em>Archimedes</em>’ solids leading to effective filling of the polyhedron by its in-sphere and therefore the highest volume ratio of the selected examples. The smallest ratio was found for the Great Pyramid. A regression analysis delivers the highly reliable volume ratio relation <img src="Edit_79e766ce-5580-4ae0-a706-570e0f3f1bd8.bmp" alt="" />, where <em>nF</em> represents the number of polyhedron faces and b approximates the silver mean. For less-symmetrical solids with a unique axis (tetragonal pyramids) the in-sphere can be replaced by a biaxial ellipsoid of maximum volume to adjust the <em>R</em><sub><em>V</em></sub> relation more reliably.
文摘When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric environment will produce a variety of adverse effects on the signal. The interference produced by these effects overlaps with each other, which will seriously affect the strength of the received signal. Therefore, how to effectively suppress the atmospheric turbulence effect in the random atmospheric turbulence channel, ensure the normal transmission of the signal in the atmospheric channel, and reduce the bit error rate of the communication system, is very necessary to improve the communication system. When processing the received signal, it is an important step to detect the transmitted signal by comparing the received signal with the threshold. In this paper, based on the atmospheric turbulence distribution model, the adaptive signal decision threshold is obtained through the estimation of high-order cumulant. Monte Carlo method is used to verify the performance of adaptive threshold detection. The simulation results show that the high-order cumulant estimation of atmospheric turbulence parameters can realize the adaptive change of the decision threshold with the channel condition. It is shown that the adaptive threshold detection can effectively restrain atmospheric turbulence, improve the performance of free space optical and improve the communication quality.
文摘目的验证三维多回波数据联合成像(three dimensional multi-echo data imagine combination with selective water excitation,3D MEDIC WE)和三维快速自旋回波成像(three dimensional sampling perfection with application optimized contrasts by using different flip angle evolution,3D SPACE STIR)序列在腰骶丛神经根成像中的可行性和重复性。方法将55例受试者分为腰椎无异常表现的正常对照组(20例)、单纯性腰椎间盘突出症(lumbar disc herniation,LDH)组(20例)和慢性炎性脱髓鞘性多发性神经根神经病症(chronic inflammatory demyelinating polyradiculoneuropathy,CIDP)组(15例),分别应用两种腰骶丛神经根成像,评价图像质量参数信噪比(signal to noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)和对比度(contrast ratio,CR),并验证正常对照组、CIDP组和LDH组测量神经根直径的一致性。结果两序列测得神经根直径的一致性较高(正常组r=0.95,CIDP组r=0.99,LDH组r=0.97,P<0.001),图像质量评价指标显示,3D SPACE STIR序列在SNR、CNR和CR三项指标中占优,3D MEDIC WE定性评估图像质量评分较高。两序列均能清晰显示正常腰骶丛神经根、病变所致的弥漫性形态增粗神经根以及间盘突出受挤压变形的神经根。结论3D MEDIC WE和3D SPACE STIR序列可应用于腰骶丛神经根成像,两序列对正常和异常形态、走行的神经根评估具备很高的可行性和重复性。综合考量临床图像的定性、定量评价,可择优选择恰当的序列为腰骶丛神经根成像提供影像支持。
文摘The construction of urban green space has attracted extensive attention of researchers under the background of urban sustainable development and ecological civilization construction.The research of urban green space involves ecology,geography,economics,sociology and other disciplines,among which geography has played an important role in promoting the study and practice of green space in terms of research perspectives,methods and techniques,planning and management.In this paper,the important role of urban geography in green space research is analyzed from defi nition,classifi cation to multidisciplinary background,and the research and practice progress of green space in urban geography are summarized in four aspects:characteristics and division of green space,relationship between green space and urban regional structure,service function of urban green space,and the relationship between green space and urban development.Finally,the practical achievements of green space research are illustrated from the perspective of urban geography.
基金King Saud University,Riyadh,Saudi Arabia,No.RSP-2020/31.
文摘BACKGROUND The introduction of modern diagnostic tools has transformed the field of maxillofacial radiology.Odontogenic infection and fascial space involvement have been evaluated with many diagnostic tools,including ultrasonography(USG)and magnetic resonance imaging(MRI).AIM To explore USG as an alternative model to MRI in the detection of fascial space spread of odontogenic infections.METHODS Among 20 patients,50 fascial spaces were clinically diagnosed with odontogenic infection and included in this prospective study.Fascial space infection involvement was examined by USG and MRI.Results were compared for both and confirmed by microbiological testing.RESULTS Ultrasonography identified 42(84%)of 50 involved fascial spaces.Whereas MRI identified all 50(100%).USG could stage the infections from edematous change to cellulitis to complete abscess formation.CONCLUSION MRI was superior in recognizing deep fascial space infections compared to USG.However, USG is a significant addition and has a definite role in prognosticatingthe stage of infection and exact anatomic location in superficial space infections.
基金Supported by Fundamental Research Funds for the Central Universities of China(N170504015,N182410008-1)。
文摘Hawking-Page phase transitions between the thermal anti-de Sitter vacuum and charged black holes sur・rounded by quintessence are studied in the extended phase space.The quintessence field,with the state parameter-1<w<-1/3,modifies the temperature and the Gibbs free energy of a black hole.The phase transition temperature Thp and the Gibbs free energy G are first analytically investigated for the special case of w=-2/3,and then,the results of numerical simulations are shown for general w.The phase transition temperature Thp increases with pressure and decreases with electric potential.In addition,Thp significantly decreases owing to the quintessence field,which generates negative pressure around the black hole.
基金supported by National Natural Science Foundation of China(Grant Nos.11371093,11431009 and 11661131004)supported by National Natural Science Foundation of China(Grant No.11028104)。
文摘In this article,we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology,such as small covers,quasi-toric manifolds and(real)moment-angle manifolds;especially for the cases of small covers and quasi-toric manifolds.These kinds of orbit configuration spaces have non-free group actions,and they are all noncompact,but still built via simple convex polytopes.We obtain an explicit formula of the Euler characteristic for orbit configuration spaces of small covers and quasi-toric manifolds in terms of the h-vector of a simple convex polytope.As a by-product of our method,we also obtain a formula of the Euler characteristic for the classical configuration space,which generalizes the Félix-Thomas formula.In addition,we also study the homotopy type of such orbit configuration spaces.In particular,we determine an equivariant strong deformation retraction of the orbit configuration space of 2 distinct orbit-points in a small cover or a quasi-toric manifold,which allows to further study the algebraic topology of such an orbit configuration space by using the Mayer-Vietoris spectral sequence.
文摘The paper belongs to the sphere of quantum physics, physics of waves and physical fields, in particular—to the gravitation. Their study provides a better understanding of the problems of natural sciences at all levels, from elementary particles, to Universe as a whole. Therefore, the solution of these problems is an urgent and important task, which to the works of many generations of scientists of the world was dedicated. However, they have not been fully resolved. In well-known works, including general relativity, determination of the wave and energy parameters of the gravitational field of the Universe and their numerical values are absent. Solutions found are limited to tensor equations of a general form, which allows their interpretation of over a wide range. Other disadvantages of famous models are: 1) the voluminous world of the Universe reduced to the planes on which space objects and other objects move, sagging planes due to their own mass;2) signs of “top” and “bottom” of the system, which are not in the real Universe, just as they are not on Earth and not in the Solar system;3) the formation of “voids” between the object and the curved space and others. Main goals of the work to identify these contradictions and find ways to resolve them are performed. The main difference and the scientific novelty of the work performed are the justification of the gravity model based on a rigorous determination of the wave and energy parameters of the gravitational field of the Universe and their numerical values. The initial parameters of this worked—is the frequency oscillation <em>ν</em><sub><em>G</em></sub> of the waves of the gravitational field (Nastasenko’s constant) found in 2011. <strong>Research Results:</strong> Knowing <em>ν</em><sub><em>G</em></sub> can find all wave parameters of the gravitational field and their numerical values. The proposed new spatial-wave model of the action of gravity is based on the wave parameters of the gravitational fields of material objects. In the framewor