Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up t...Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up to 7G.Furthermore,it improves the array gain and directivity,increasing the detection range and angular resolution of radar systems.This study proposes two highly efficient SLL reduction techniques.These techniques are based on the hybridization between either the single convolution or the double convolution algorithms and the genetic algorithm(GA)to develop the Conv/GA andDConv/GA,respectively.The convolution process determines the element’s excitations while the GA optimizes the element spacing.For M elements linear antenna array(LAA),the convolution of the excitation coefficients vector by itself provides a new vector of excitations of length N=(2M−1).This new vector is divided into three different sets of excitations including the odd excitations,even excitations,and middle excitations of lengths M,M−1,andM,respectively.When the same element spacing as the original LAA is used,it is noticed that the odd and even excitations provide a much lower SLL than that of the LAA but with amuch wider half-power beamwidth(HPBW).While the middle excitations give the same HPBWas the original LAA with a relatively higher SLL.Tomitigate the increased HPBWof the odd and even excitations,the element spacing is optimized using the GA.Thereby,the synthesized arrays have the same HPBW as the original LAA with a two-fold reduction in the SLL.Furthermore,for extreme SLL reduction,the DConv/GA is introduced.In this technique,the same procedure of the aforementioned Conv/GA technique is performed on the resultant even and odd excitation vectors.It provides a relatively wider HPBWthan the original LAA with about quad-fold reduction in the SLL.展开更多
For many years now," autonomy" in learning has been a topic of widespread discussion in educational field.Accordingly,it is Henry Holec who introduced learner autonomy to the field of second language in his ...For many years now," autonomy" in learning has been a topic of widespread discussion in educational field.Accordingly,it is Henry Holec who introduced learner autonomy to the field of second language in his project report to the Council of Europe in 1981.Motivation is also a widely used psychological term in our daily life and research.Both learner autonomy and motivation are important factors in influencing learning effects.Many researchers conduct studies on learner autonomy and motivation.There are also some studies on the correlation between learner autonomy and motivation in SLL(Second Language Learning).However,few of them focus on the effect of learner autonomy on motivation.Thus,it makes an attempt to investigate whether learner autonomy has an enhancement effect on motivation.It combines motivation and learner autonomy together to find some effective and efficient ways of promoting foreign or second language learning.In another way,it enriches learner autonomy research.It holds that learner autonomy is a very important factor in influencing motivation.It will make a combination between learner autonomy and motivation in SLL to find some new ways of promoting learners' motivation and learning efficiency.A survey methodology has been employed which consists of qualitative and quantitative methods.Specifically,both questionnaire and interview have been conducted in the research.展开更多
Grammatical Metaphor differs from traditional metaphor in terms of lexical density and structural complesity.It casts a big influence on Input in SLL due to difficulties in comprehensibility.
A low-sidelobe-level( SLL) and wideband linear dielectric resonator antenna( DRA) array is proposed for 60 GHz millimeter wave communication. The array consists of 10 wideband DRAs which work at 60 GHz and it is fed b...A low-sidelobe-level( SLL) and wideband linear dielectric resonator antenna( DRA) array is proposed for 60 GHz millimeter wave communication. The array consists of 10 wideband DRAs which work at 60 GHz and it is fed by a Chebyshev feeding network to get a low SLL. To avoid the influence from the feeding network,a U-shaped substrate and a conformal ground are used,which can separate the DRA array and the feeding network. The parameter analysis and simulated results are presented.展开更多
In this paper,the author has reviewed the role of input,interaction and output in second language learning.Then she cites examples from her own teaching experiences to illustrate her opinion:first,our teacher should f...In this paper,the author has reviewed the role of input,interaction and output in second language learning.Then she cites examples from her own teaching experiences to illustrate her opinion:first,our teacher should fully understand the students’English level and their needs,adopt the appropriate teaching methods which can stimulate students’interest and motivation;second,we should emphasize the roles and functions of input,interaction and output in SLL;last but not the least,in the course of teaching we should give students enough input and provide more opportunities for interaction so as to encourage students to speak English,thus the frequency of language output should be greatly increased.展开更多
For the anti-interference/denoise purpose,it usually requires minimizing the sidelobe level(SLL)of a wide-beam pattern with a desired low nulling level(NL)in the nulling region.To realize such an objective,the shaped-...For the anti-interference/denoise purpose,it usually requires minimizing the sidelobe level(SLL)of a wide-beam pattern with a desired low nulling level(NL)in the nulling region.To realize such an objective,the shaped-beam pattern synthesis(SBPS)is the most commonly used approach.However,since the SBPS problem focuses on synthesizing a predetermined beam shape,the minimum SLL via this approach cannot ensure to obtain the maximum power gain.Conversely,it cannot obtain the lowest SLL with a certain power gain requirement.Based on such consideration,this paper tries to further minimize SLL of a wide-beam pattern with a desired low NL nulling region,by solving the power gain pattern synthesis(PGPS)problem.The PGPS problem selects the array excitation by directly optimizing the power gain.Hence,it has the potential to reduce SLL,when achieving the equal mainlobe power gain constraint via SBPS.An iterative algorithm which converts the primal optimization problem into convex sub-problems is proposed,resulting in an effective problem-solving scheme.Numerical simulations demonstrate the proposed algorithm can obtain about 10-dB lower SLL than the existing algorithms.展开更多
利用扫描激光线源(scaing laser line source,SLLS)技术,提出一种金属表面缺陷位置检测方法,并搭建实验平台,实验研究该检测方法对金属表面缺陷位置的检测效果;方法中利用扫描激光线源技术对样品表面进行扫查,在样品内部激发超声信号,...利用扫描激光线源(scaing laser line source,SLLS)技术,提出一种金属表面缺陷位置检测方法,并搭建实验平台,实验研究该检测方法对金属表面缺陷位置的检测效果;方法中利用扫描激光线源技术对样品表面进行扫查,在样品内部激发超声信号,采用双波混合干涉方法实现对激发信号的探测,根据激发的瑞利波和反射回波与缺陷位置的关系,确定激发点和探测点到缺陷的距离,从而确定缺陷的位置;实验研究中分别以线源位置和探测点位置为基点确定缺陷位置,结果表明以探测点位置确定缺陷位置时,定位相对误差为0.23%。展开更多
基金Research Supporting Project Number(RSPD2023R 585),King Saud University,Riyadh,Saudi Arabia.
文摘Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up to 7G.Furthermore,it improves the array gain and directivity,increasing the detection range and angular resolution of radar systems.This study proposes two highly efficient SLL reduction techniques.These techniques are based on the hybridization between either the single convolution or the double convolution algorithms and the genetic algorithm(GA)to develop the Conv/GA andDConv/GA,respectively.The convolution process determines the element’s excitations while the GA optimizes the element spacing.For M elements linear antenna array(LAA),the convolution of the excitation coefficients vector by itself provides a new vector of excitations of length N=(2M−1).This new vector is divided into three different sets of excitations including the odd excitations,even excitations,and middle excitations of lengths M,M−1,andM,respectively.When the same element spacing as the original LAA is used,it is noticed that the odd and even excitations provide a much lower SLL than that of the LAA but with amuch wider half-power beamwidth(HPBW).While the middle excitations give the same HPBWas the original LAA with a relatively higher SLL.Tomitigate the increased HPBWof the odd and even excitations,the element spacing is optimized using the GA.Thereby,the synthesized arrays have the same HPBW as the original LAA with a two-fold reduction in the SLL.Furthermore,for extreme SLL reduction,the DConv/GA is introduced.In this technique,the same procedure of the aforementioned Conv/GA technique is performed on the resultant even and odd excitation vectors.It provides a relatively wider HPBWthan the original LAA with about quad-fold reduction in the SLL.
文摘For many years now," autonomy" in learning has been a topic of widespread discussion in educational field.Accordingly,it is Henry Holec who introduced learner autonomy to the field of second language in his project report to the Council of Europe in 1981.Motivation is also a widely used psychological term in our daily life and research.Both learner autonomy and motivation are important factors in influencing learning effects.Many researchers conduct studies on learner autonomy and motivation.There are also some studies on the correlation between learner autonomy and motivation in SLL(Second Language Learning).However,few of them focus on the effect of learner autonomy on motivation.Thus,it makes an attempt to investigate whether learner autonomy has an enhancement effect on motivation.It combines motivation and learner autonomy together to find some effective and efficient ways of promoting foreign or second language learning.In another way,it enriches learner autonomy research.It holds that learner autonomy is a very important factor in influencing motivation.It will make a combination between learner autonomy and motivation in SLL to find some new ways of promoting learners' motivation and learning efficiency.A survey methodology has been employed which consists of qualitative and quantitative methods.Specifically,both questionnaire and interview have been conducted in the research.
文摘Grammatical Metaphor differs from traditional metaphor in terms of lexical density and structural complesity.It casts a big influence on Input in SLL due to difficulties in comprehensibility.
基金Supported by the National Natural Science Foundation of China(No.61171031)
文摘A low-sidelobe-level( SLL) and wideband linear dielectric resonator antenna( DRA) array is proposed for 60 GHz millimeter wave communication. The array consists of 10 wideband DRAs which work at 60 GHz and it is fed by a Chebyshev feeding network to get a low SLL. To avoid the influence from the feeding network,a U-shaped substrate and a conformal ground are used,which can separate the DRA array and the feeding network. The parameter analysis and simulated results are presented.
文摘In this paper,the author has reviewed the role of input,interaction and output in second language learning.Then she cites examples from her own teaching experiences to illustrate her opinion:first,our teacher should fully understand the students’English level and their needs,adopt the appropriate teaching methods which can stimulate students’interest and motivation;second,we should emphasize the roles and functions of input,interaction and output in SLL;last but not the least,in the course of teaching we should give students enough input and provide more opportunities for interaction so as to encourage students to speak English,thus the frequency of language output should be greatly increased.
基金supported by the Natural Science Foundation of Sichuan Province under Grant No.2022NSFSC0564the National Natural Science Foundation of China under Grants No.U20B2043 and No.62001095.
文摘For the anti-interference/denoise purpose,it usually requires minimizing the sidelobe level(SLL)of a wide-beam pattern with a desired low nulling level(NL)in the nulling region.To realize such an objective,the shaped-beam pattern synthesis(SBPS)is the most commonly used approach.However,since the SBPS problem focuses on synthesizing a predetermined beam shape,the minimum SLL via this approach cannot ensure to obtain the maximum power gain.Conversely,it cannot obtain the lowest SLL with a certain power gain requirement.Based on such consideration,this paper tries to further minimize SLL of a wide-beam pattern with a desired low NL nulling region,by solving the power gain pattern synthesis(PGPS)problem.The PGPS problem selects the array excitation by directly optimizing the power gain.Hence,it has the potential to reduce SLL,when achieving the equal mainlobe power gain constraint via SBPS.An iterative algorithm which converts the primal optimization problem into convex sub-problems is proposed,resulting in an effective problem-solving scheme.Numerical simulations demonstrate the proposed algorithm can obtain about 10-dB lower SLL than the existing algorithms.
文摘利用扫描激光线源(scaing laser line source,SLLS)技术,提出一种金属表面缺陷位置检测方法,并搭建实验平台,实验研究该检测方法对金属表面缺陷位置的检测效果;方法中利用扫描激光线源技术对样品表面进行扫查,在样品内部激发超声信号,采用双波混合干涉方法实现对激发信号的探测,根据激发的瑞利波和反射回波与缺陷位置的关系,确定激发点和探测点到缺陷的距离,从而确定缺陷的位置;实验研究中分别以线源位置和探测点位置为基点确定缺陷位置,结果表明以探测点位置确定缺陷位置时,定位相对误差为0.23%。
