AIM:To evaluate the effects of refractive errors and binocular vision anomalies on the quality of life(QOL)of university students.METHODS:This cross-sectional analytical study was conducted on university students usin...AIM:To evaluate the effects of refractive errors and binocular vision anomalies on the quality of life(QOL)of university students.METHODS:This cross-sectional analytical study was conducted on university students using simple random sampling.Objective refraction,ocular alignment,vergence and accommodative performance were measured and assessed in all participants.Data on QOL were collected using the College of Optometrists in Vision Development-Quality of Life(COVD-QOL)Questionnaire.The effect of mentioned parameters on the QOL were evaluated.RESULTS:Totally 726 students with mean age of 21.35±1.88y were evaluated in this study,51.5%of whom were female.Esophoria was caused significantly lower QOL in the domains of somatic symptoms and occupationalphysical symptoms(P<0.05);Besides,esotropia decreased QOL in domains of somatic symptoms P=0.002 and psychological factors(P=0.023).Students with accommodation insufficiency experienced more symptoms in all domains(P<0.05)except for psychological factors(P=0.07).Increasing in the near point of convergence and accommodation and decreases QOL and increasing accommodative facility increases QOL(all P<0.05).Myopia and astigmatism cause decrease in QOL(both P<0.05),but hyperopic students had better QOL in comparison with others(P<0.05).CONCLUSION:Screening programs and treatment of refractive errors and binocular vision anomalies,especially phoria and accommodative insufficiency,positively impact the QOL and academic achievements of university students.展开更多
Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional load...Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional loaded tooth contact analysis(3D-LTCA)method which can consider tooth modification and coupling assembly errors is proposed,and mesh stiffness calculated by proposed method is verified by MASTA software.Secondly,based on neural network,the surrogate model(SM)that maps the relationship between modification parameters and mesh mechanical parameters is established,and its accuracy is verified.Finally,SM is introduced to establish an optimization model with the target of minimizing mesh stiffness variations and obtaining more even load distribution on mesh surface.The results show that even considering training time,the efficiency of gear pair optimization by surrogate model is still much higher than that by LTCA method.After optimization,the mesh stiffness fluctuation of gear pair with coupling assembly error is reduced by 34.10%,and difference in average contact stresses between left and right regions of the mesh surface is reduced by 62.84%.展开更多
Objective:To evaluate the level of understanding(knowledge),beliefs(attitude),and behavior(practice)of staff nurses toward medication errors(MEs).Methods:Self-administered questionnaires were distributed to nursing pr...Objective:To evaluate the level of understanding(knowledge),beliefs(attitude),and behavior(practice)of staff nurses toward medication errors(MEs).Methods:Self-administered questionnaires were distributed to nursing professionals who had at least 1 year of work experience.Each questionnaire contained 19 items assessing“knowledge,”“attitude,”and“practice”attributes toward MEs.Results:Responses from 47 nursing respondents were included for the final analysis.The mean knowledge score was 3.8±1.1(out of 6);66%and 79%of the respondents had awareness of medication repor ting systems and interventions in preventing MEs,respectively.Lack of adequate knowledge in recognizing MEs(P=0.003),or presuming MEs are not as important enough to be reported(P=0.002),was considered as the major reason for under-repor ting of MEs.Nurses with higher knowledge score were against administration of medication through a different route than that prescribed by the physician(P=0.023),and tried to rectify an ME(P=0.020)and stayed with the patient until an oral medication had been swallowed(P=0.037).Conclusions:The nursing professionals were aware of the ME repor ting system and methods to prevent the occurrence of MEs.They also exhibited a positive attitude and followed optimal practices in controlling MEs.展开更多
The influences of machining and misalignment errors play a very critical role in the performance of the anti-backlash double-roller enveloping hourglass worm gear(ADEHWG).However,a corresponding efficient method for e...The influences of machining and misalignment errors play a very critical role in the performance of the anti-backlash double-roller enveloping hourglass worm gear(ADEHWG).However,a corresponding efficient method for eliminating or reducing these errors on the tooth profile of the ADEHWG is seldom reported.The gear engagement equation and tooth profile equation for considering six different errors that could arise from the machining and gear misalignment are derived from the theories of differential geometry and gear meshing.Also,the tooth contact analysis(TCA) is used to systematically investigate the influence of the machining and misalignment errors on the contact curves and the tooth profile by means of numerical analysis and three-dimensional solid modeling.The research results show that vertical angular misalignment of the worm wheel(Δβ) has the strongest influences while the tooth angle error(Δα) has the weakest influences on the contact curves and the tooth profile.A novel efficient approach is proposed and used to minimize the effect of the errors in manufacturing by changing the radius of the grinding wheel and the approaching point of contact.The results from the TCA and the experiment demonstrate that this tooth profile design modification method can indeed reduce the machining and misalignment errors.This modification design method is helpful in understanding the manufacturing technology of the ADEHWG.展开更多
Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors.The crosstalk fringes generated by stray light in interferometry can affect accuracy and pote...Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors.The crosstalk fringes generated by stray light in interferometry can affect accuracy and potentially prevent the testing from proceeding normally.Position errors include the decenter error,tilt error,and distance error.During the testing process,position errors will impact the testing accuracy and the crosstalk fringes generated by stray light.To determine the specific impact of position errors,we use the concept of Hindle shell testing of a convex aspheric mirror,and propose the simulation method of crosstalk fringes in null compensation interferometry.We also propose evaluation indices of crosstalk fringes in interferometry and simulate the influence of position errors on the crosstalk fringes.This work aims to help improve the design of compensation interferometry schemes,enhance the feasibility of the design,reduce engineering risks,and improve efficiency.展开更多
The fragility and stochastic behavior of quantum sources make it crucial to witness the topology of quantum networks.Most previous theoretical methods are based on perfect assumptions of quantum measurements.In this w...The fragility and stochastic behavior of quantum sources make it crucial to witness the topology of quantum networks.Most previous theoretical methods are based on perfect assumptions of quantum measurements.In this work,we propose a method to witness network topology under imperfect assumptions of quantum measurements.We show that the discrimination between star and triangle networks depends on the specific error tolerances of local measurements.This extends recent results for witnessing the triangle network[Phys.Rev.Lett.132240801(2024)].展开更多
To address the significant degradation of Space-Time Adaptive Processing(STAP)performance when the array elements have mutual coupling and gain/phase errors,a STAP algorithm with adaptive calibration for the above two...To address the significant degradation of Space-Time Adaptive Processing(STAP)performance when the array elements have mutual coupling and gain/phase errors,a STAP algorithm with adaptive calibration for the above two array errors is proposed in this article.First,based on a defined error matrix that simultaneously considers both array mutual coupling and gain/phase errors,a STAP signal model including these errors is given.Then,utilizing the defined signal model,it is demonstrated that the estimation of the defined error matrix can be formulized as a standard convex optimization problem with the low-rank structure of the clutter covariance matrix and the subspace projection theory.Once the defined error matrix is estimated by solving the convex optimization problem,it is illustrated that a STAP method with adaptive calibration of the mutual coupling and gain/phase errors is coined.Analyses also show that the proposed adaptive calibration algorithm only needs one training sample to construct the adaptive weight vector.Therefore,it can achieve a good detection performance even with severe non-homogeneous clutter environments.Finally,the simulation experiments verify the effectiveness of the proposed algorithm and the correctness of the analytical results.展开更多
Recently,the NGPON2 standards organization has decided to deploy LDPC code in upstream and downstream channels in next-generation Ethernet passive optical network(NG-EPON)systems.However,PON upstream channels operate ...Recently,the NGPON2 standards organization has decided to deploy LDPC code in upstream and downstream channels in next-generation Ethernet passive optical network(NG-EPON)systems.However,PON upstream channels operate in burst-mode,hence the turn-on effects in optical network units(ONUs)may introduce burst errors,which are difficult for LDPC to deal with.One of the solutions is introducing an interleaver to convert consecutive burst errors into separate random errors.The traditional interleavers such as the block interleaver and the random interleaver,only consider dispersing the consecutive errors.In this paper,we present a design methodology for channel-adaptive interleaving pattern by joint optimizing of interleaving and LDPC decoding in PON systems deploying LDPC codes.After determining the interleaving pattern where the bits can be recovered with more reliable messages during LDPC iterative decoding,we map the bits from the potential locations of burst errors to the interleaving positions.By doing so,we can not only disperse the burst errors but also make full use of the LDPC code to improve its decoding performance.The numerical results show that the proposed interleaving scheme has a better performance under any burst-error length.展开更多
·AIM: To review existing data for the prevalence of corrected, uncorrected, and inadequately corrected refractive errors and spectacle wear in Hungary.·METHODS: Data from two nationwide cross-sectional studi...·AIM: To review existing data for the prevalence of corrected, uncorrected, and inadequately corrected refractive errors and spectacle wear in Hungary.·METHODS: Data from two nationwide cross-sectional studies were analysed. The Rapid Assessment of Avoidable Blindness study collected population-based representative national data on the prevalence of visual impairment due to uncorrected refractive errors and spectacle coverage in 3523 people aged ≥50y(Group I). The Comprehensive Health Test Program of Hungary provided data on the use of spectacles in 80 290 people aged ≥18y(Group Ⅱ).·RESULTS: In Group I, almost half of the survey population showed refractive errors for distant vision, about 10% of which were uncorrected(3.2% of all male participants and 5.0% of females). The distance spectacle coverage was 90.7%(91.9% in males;90.2% in females). The proportion of inadequate distance spectacles was found to be 33.1%. Uncorrected presbyopia was found in 15.7% of participants. In all age groups(Group Ⅱ), 65.4% of females and 56.0% of males used distance spectacles,and approximately 28.9% of these spectacles were found to be inappropriate for dioptric power(with 0.5 dioptres or more). The prevalence of inaccurate distance spectacles was significantly higher in older age groups(71y and above) in both sexes.·CONCLUSION: According to this population-based data, uncorrected refractive errors are not rare in Hungary. Despite recent national initiatives, fur ther steps are required to reduce uncorrected refractive errors and associated negative effects on vision, such as avoidable visual impairment.展开更多
ABSTRACT The impact of both initial and parameter errors on the spring predictability barrier （SPB） is investigated using the Zebiak Cane model （ZC model）. Previous studies have shown that initial errors contribu...ABSTRACT The impact of both initial and parameter errors on the spring predictability barrier （SPB） is investigated using the Zebiak Cane model （ZC model）. Previous studies have shown that initial errors contribute more to the SPB than parameter errors in the ZC model. Although parameter errors themselves are less important, there is a possibility that nonlinear interactions can occur between the two types of errors, leading to larger prediction errors compared with those induced by initial errors alone. In this case, the impact of parameter errors cannot be overlooked. In the present paper, the optimal combination of these two types of errors [i.e., conditional nonlinear optimal perturbation （CNOP） errors] is calculated to investigate whether this optimal error combination may cause a more notable SPB phenomenon than that caused by initial errors alone. Using the CNOP approach, the CNOP errors and CNOP-I errors （optimal errors when only initial errors are considered） are calculated and then three aspects of error growth are compared： （1） the tendency of the seasonal error growth; （2） the prediction error of the sea surface temperature anomaly; and （3） the pattern of error growth. All three aspects show that the CNOP errors do not cause a more significant SPB than the CNOP-I errors. Therefore, this result suggests that we could improve the prediction of the E1 Nifio during spring by simply focusing on reducing the initial errors in this model.展开更多
This paper investigated the spelling errors made by university students in Hong Kong.By analyzing the spelling errors in the untimed essays and exam scripts,we found that students are prone to make more spelling mista...This paper investigated the spelling errors made by university students in Hong Kong.By analyzing the spelling errors in the untimed essays and exam scripts,we found that students are prone to make more spelling mistakes in exam scripts,the same type of errors occur in both of the two kinds of texts;and their ranks of the frequency also are the same.展开更多
Based on the questionnaire, this study found that :1) Elementary learners were inclined to commit more global errors compared to their local errors, whilst advanced learners make more local errors; 2) Interlingual fac...Based on the questionnaire, this study found that :1) Elementary learners were inclined to commit more global errors compared to their local errors, whilst advanced learners make more local errors; 2) Interlingual factors were more influential than intralingual factors in elementary learners' error making, but for advanced learners, intralingual factors played relatively a much more important role in error making; 3) Elementary learners preferred explicit correction whilst advanced learners favoured im?plicit correction in question-asking.展开更多
On the basis of the theories of psycholinguistic perspective in language teaching and communicative approach in language learning,the author of this paper analysed briefly some tangible errors for the Chinese students...On the basis of the theories of psycholinguistic perspective in language teaching and communicative approach in language learning,the author of this paper analysed briefly some tangible errors for the Chinese students in their reading comprehension in line with his own teaching experiences. The aim of the paper is to overcome the obstacles existing between the author’ s text writers and the text readers and to enable the latter to become effective readers.展开更多
This paper presents a novel approach to identify and correct the gross errors in the microelectromechanical system （MEMS） gyroscope used in ground vehicles by means of time series analysis. According to the characte...This paper presents a novel approach to identify and correct the gross errors in the microelectromechanical system （MEMS） gyroscope used in ground vehicles by means of time series analysis. According to the characteristics of autocorrelation function （ACF） and partial autocorrelation function （PACF）, an autoregressive integrated moving average （ARIMA） model is roughly constructed. The rough model is optimized by combining with Akaike＇s information criterion （A/C）, and the parameters are estimated based on the least squares algorithm. After validation testing, the model is utilized to forecast the next output on the basis of the previous measurement. When the difference between the measurement and its prediction exceeds the defined threshold, the measurement is identified as a gross error and remedied by its prediction. A case study on the yaw rate is performed to illustrate the developed algorithm. Experimental results demonstrate that the proposed approach can effectively distinguish gross errors and make some reasonable remedies.展开更多
This paper proposes a steady-state errors correction(SSEC)method for eliminating measurement errors.This method is based on the detections of error signal E(s)and output C(s)which generate an expected output R(s).In c...This paper proposes a steady-state errors correction(SSEC)method for eliminating measurement errors.This method is based on the detections of error signal E(s)and output C(s)which generate an expected output R(s).In comparison with the conventional solutions which are based on detecting the expected output R(s)and output C(s)to obtain error signal E(s),the measurement errors are eliminated even the error might be at a significant level.Moreover,it is possible that the individual debugging by regulating the coefficient K for every member of the multiple objectives achieves the optimization of the open loop gain.Therefore,this simple method can be applied to the weak coupling and multiple objectives system,which is usually controlled by complex controller.The principle of eliminating measurement errors is derived analytically,and the advantages comparing with the conventional solutions are depicted.Based on the SSEC method analysis,an application of this method for an active power filter(APF)is investigated and the effectiveness and viability of the scheme are demonstrated through the simulation and experimental verifications.展开更多
Before cognitive approach came into being in the 1960s, errors in L2 learning were always regarded as signs of failure which needed immediate attention from the teacher. By analyzing a student＇s writing, this paper t...Before cognitive approach came into being in the 1960s, errors in L2 learning were always regarded as signs of failure which needed immediate attention from the teacher. By analyzing a student＇s writing, this paper tries to elaborate on the roles that errors can play in L2 learning process.展开更多
The research on the common errors in junior English writings reflects the categories of errors, resources of errors, and how to do with errors in effective ways. Errors are divided into two types: intralingual errors ...The research on the common errors in junior English writings reflects the categories of errors, resources of errors, and how to do with errors in effective ways. Errors are divided into two types: intralingual errors and interlingual errors. The research finds that Chinese junior students depend heavily on their native language in English writing and finds out some effective strate gies avoiding errors in writing.展开更多
This paper analyzes the lexical errors that students make in their written work.The errors are classified,and their causes are traced.The implications of the analysis are also provided in the paper.
The software Wordsmith has been commonly used in corpus linguistics.In this paper,the author used the tool of Concord in Wordsmith to analyze various errors made by a student.Five passages made by the students are use...The software Wordsmith has been commonly used in corpus linguistics.In this paper,the author used the tool of Concord in Wordsmith to analyze various errors made by a student.Five passages made by the students are used.After annotating on the errors,the author uses Concord to sort out each error maker and made classification chart of the errors.All the errors are classified into two categories:errors caused by carelessness and by language ability.After analyzing,there are mainly three kinds of errors and in the first category and five kinds of errors in the second category.展开更多
This paper proposes a new approach to design pinion machine tool-settings for spiral bevel gears by controlling contact path and transmission errors. It is based on the satisfaction of contact condition of three given...This paper proposes a new approach to design pinion machine tool-settings for spiral bevel gears by controlling contact path and transmission errors. It is based on the satisfaction of contact condition of three given control points on the tooth surface. The three meshing points are controlled to be on a predesigned straight contact path that meets the pre-designed parabolic function of transmission errors. Designed separately, the magnitude of transmission errors and the orientation of the contact path are subjected to precise control. In addition, in order to meet the manufacturing requirements, we suggest to modify the values of blank offset, one of the pinion machine tool-settings, and redesign pinion ma- chine tool-settings to ensure that the magnitude and the geometry of transmission errors should not be influenced apart from minor effects on the predesigned straight contact path. The proposed approach together with its ideas has been proven by a numerical example and the manufacturing practice of a pair of spiral bevel gears.展开更多
文摘AIM:To evaluate the effects of refractive errors and binocular vision anomalies on the quality of life(QOL)of university students.METHODS:This cross-sectional analytical study was conducted on university students using simple random sampling.Objective refraction,ocular alignment,vergence and accommodative performance were measured and assessed in all participants.Data on QOL were collected using the College of Optometrists in Vision Development-Quality of Life(COVD-QOL)Questionnaire.The effect of mentioned parameters on the QOL were evaluated.RESULTS:Totally 726 students with mean age of 21.35±1.88y were evaluated in this study,51.5%of whom were female.Esophoria was caused significantly lower QOL in the domains of somatic symptoms and occupationalphysical symptoms(P<0.05);Besides,esotropia decreased QOL in domains of somatic symptoms P=0.002 and psychological factors(P=0.023).Students with accommodation insufficiency experienced more symptoms in all domains(P<0.05)except for psychological factors(P=0.07).Increasing in the near point of convergence and accommodation and decreases QOL and increasing accommodative facility increases QOL(all P<0.05).Myopia and astigmatism cause decrease in QOL(both P<0.05),but hyperopic students had better QOL in comparison with others(P<0.05).CONCLUSION:Screening programs and treatment of refractive errors and binocular vision anomalies,especially phoria and accommodative insufficiency,positively impact the QOL and academic achievements of university students.
基金Project(11972112)supported by the National Natural Science Foundation of ChinaProject(N2103024)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(J2019-IV-0018-0086)supported by the National Science and Technology Major Project,China。
文摘Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional loaded tooth contact analysis(3D-LTCA)method which can consider tooth modification and coupling assembly errors is proposed,and mesh stiffness calculated by proposed method is verified by MASTA software.Secondly,based on neural network,the surrogate model(SM)that maps the relationship between modification parameters and mesh mechanical parameters is established,and its accuracy is verified.Finally,SM is introduced to establish an optimization model with the target of minimizing mesh stiffness variations and obtaining more even load distribution on mesh surface.The results show that even considering training time,the efficiency of gear pair optimization by surrogate model is still much higher than that by LTCA method.After optimization,the mesh stiffness fluctuation of gear pair with coupling assembly error is reduced by 34.10%,and difference in average contact stresses between left and right regions of the mesh surface is reduced by 62.84%.
文摘Objective:To evaluate the level of understanding(knowledge),beliefs(attitude),and behavior(practice)of staff nurses toward medication errors(MEs).Methods:Self-administered questionnaires were distributed to nursing professionals who had at least 1 year of work experience.Each questionnaire contained 19 items assessing“knowledge,”“attitude,”and“practice”attributes toward MEs.Results:Responses from 47 nursing respondents were included for the final analysis.The mean knowledge score was 3.8±1.1(out of 6);66%and 79%of the respondents had awareness of medication repor ting systems and interventions in preventing MEs,respectively.Lack of adequate knowledge in recognizing MEs(P=0.003),or presuming MEs are not as important enough to be reported(P=0.002),was considered as the major reason for under-repor ting of MEs.Nurses with higher knowledge score were against administration of medication through a different route than that prescribed by the physician(P=0.023),and tried to rectify an ME(P=0.020)and stayed with the patient until an oral medication had been swallowed(P=0.037).Conclusions:The nursing professionals were aware of the ME repor ting system and methods to prevent the occurrence of MEs.They also exhibited a positive attitude and followed optimal practices in controlling MEs.
基金supported by National Natural Science Foundation of China(Grant Nos. 50775190No.51275425)+2 种基金Spring Sunshine Plan of Ministry of Education of China(Grant No. 10202258)Talent Introduction of Xihua UniversityChina(Grant No. Z1220217)
文摘The influences of machining and misalignment errors play a very critical role in the performance of the anti-backlash double-roller enveloping hourglass worm gear(ADEHWG).However,a corresponding efficient method for eliminating or reducing these errors on the tooth profile of the ADEHWG is seldom reported.The gear engagement equation and tooth profile equation for considering six different errors that could arise from the machining and gear misalignment are derived from the theories of differential geometry and gear meshing.Also,the tooth contact analysis(TCA) is used to systematically investigate the influence of the machining and misalignment errors on the contact curves and the tooth profile by means of numerical analysis and three-dimensional solid modeling.The research results show that vertical angular misalignment of the worm wheel(Δβ) has the strongest influences while the tooth angle error(Δα) has the weakest influences on the contact curves and the tooth profile.A novel efficient approach is proposed and used to minimize the effect of the errors in manufacturing by changing the radius of the grinding wheel and the approaching point of contact.The results from the TCA and the experiment demonstrate that this tooth profile design modification method can indeed reduce the machining and misalignment errors.This modification design method is helpful in understanding the manufacturing technology of the ADEHWG.
基金the National Key Research and Development Program of China(2022YFB3403404)the Youth Innovation Promotion Association,CAS(2022213)the National Natural Science Foundation of China(62127901 and 62305334).
文摘Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors.The crosstalk fringes generated by stray light in interferometry can affect accuracy and potentially prevent the testing from proceeding normally.Position errors include the decenter error,tilt error,and distance error.During the testing process,position errors will impact the testing accuracy and the crosstalk fringes generated by stray light.To determine the specific impact of position errors,we use the concept of Hindle shell testing of a convex aspheric mirror,and propose the simulation method of crosstalk fringes in null compensation interferometry.We also propose evaluation indices of crosstalk fringes in interferometry and simulate the influence of position errors on the crosstalk fringes.This work aims to help improve the design of compensation interferometry schemes,enhance the feasibility of the design,reduce engineering risks,and improve efficiency.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12271394 and 62172341)the Sichuan Natural Science Foundation(Grant Nos.2024NSFSC1365 and 2024NSFSC1375)。
文摘The fragility and stochastic behavior of quantum sources make it crucial to witness the topology of quantum networks.Most previous theoretical methods are based on perfect assumptions of quantum measurements.In this work,we propose a method to witness network topology under imperfect assumptions of quantum measurements.We show that the discrimination between star and triangle networks depends on the specific error tolerances of local measurements.This extends recent results for witnessing the triangle network[Phys.Rev.Lett.132240801(2024)].
基金co-supported by the National Natural Science Foundation of China(No.12374431)。
文摘To address the significant degradation of Space-Time Adaptive Processing(STAP)performance when the array elements have mutual coupling and gain/phase errors,a STAP algorithm with adaptive calibration for the above two array errors is proposed in this article.First,based on a defined error matrix that simultaneously considers both array mutual coupling and gain/phase errors,a STAP signal model including these errors is given.Then,utilizing the defined signal model,it is demonstrated that the estimation of the defined error matrix can be formulized as a standard convex optimization problem with the low-rank structure of the clutter covariance matrix and the subspace projection theory.Once the defined error matrix is estimated by solving the convex optimization problem,it is illustrated that a STAP method with adaptive calibration of the mutual coupling and gain/phase errors is coined.Analyses also show that the proposed adaptive calibration algorithm only needs one training sample to construct the adaptive weight vector.Therefore,it can achieve a good detection performance even with severe non-homogeneous clutter environments.Finally,the simulation experiments verify the effectiveness of the proposed algorithm and the correctness of the analytical results.
基金supported by National Natural Science Foundation of China(No.U21A20454).
文摘Recently,the NGPON2 standards organization has decided to deploy LDPC code in upstream and downstream channels in next-generation Ethernet passive optical network(NG-EPON)systems.However,PON upstream channels operate in burst-mode,hence the turn-on effects in optical network units(ONUs)may introduce burst errors,which are difficult for LDPC to deal with.One of the solutions is introducing an interleaver to convert consecutive burst errors into separate random errors.The traditional interleavers such as the block interleaver and the random interleaver,only consider dispersing the consecutive errors.In this paper,we present a design methodology for channel-adaptive interleaving pattern by joint optimizing of interleaving and LDPC decoding in PON systems deploying LDPC codes.After determining the interleaving pattern where the bits can be recovered with more reliable messages during LDPC iterative decoding,we map the bits from the potential locations of burst errors to the interleaving positions.By doing so,we can not only disperse the burst errors but also make full use of the LDPC code to improve its decoding performance.The numerical results show that the proposed interleaving scheme has a better performance under any burst-error length.
基金The RAAB survey was supported by the Lions Clubs International Foundation (LCIF) Sight First Research Grant Program (No.SF 1825/UND)。
文摘·AIM: To review existing data for the prevalence of corrected, uncorrected, and inadequately corrected refractive errors and spectacle wear in Hungary.·METHODS: Data from two nationwide cross-sectional studies were analysed. The Rapid Assessment of Avoidable Blindness study collected population-based representative national data on the prevalence of visual impairment due to uncorrected refractive errors and spectacle coverage in 3523 people aged ≥50y(Group I). The Comprehensive Health Test Program of Hungary provided data on the use of spectacles in 80 290 people aged ≥18y(Group Ⅱ).·RESULTS: In Group I, almost half of the survey population showed refractive errors for distant vision, about 10% of which were uncorrected(3.2% of all male participants and 5.0% of females). The distance spectacle coverage was 90.7%(91.9% in males;90.2% in females). The proportion of inadequate distance spectacles was found to be 33.1%. Uncorrected presbyopia was found in 15.7% of participants. In all age groups(Group Ⅱ), 65.4% of females and 56.0% of males used distance spectacles,and approximately 28.9% of these spectacles were found to be inappropriate for dioptric power(with 0.5 dioptres or more). The prevalence of inaccurate distance spectacles was significantly higher in older age groups(71y and above) in both sexes.·CONCLUSION: According to this population-based data, uncorrected refractive errors are not rare in Hungary. Despite recent national initiatives, fur ther steps are required to reduce uncorrected refractive errors and associated negative effects on vision, such as avoidable visual impairment.
基金jointly sponsored by the National Nature Scientific Foundation of China (Grant Nos.41230420 and 41006015)the National Basic Research Program of China (Grant No.2012CB417404)the Basic Research Program of Science and Technology Projects of Qingdao (Grant No11-1-4-95-jch)
文摘ABSTRACT The impact of both initial and parameter errors on the spring predictability barrier （SPB） is investigated using the Zebiak Cane model （ZC model）. Previous studies have shown that initial errors contribute more to the SPB than parameter errors in the ZC model. Although parameter errors themselves are less important, there is a possibility that nonlinear interactions can occur between the two types of errors, leading to larger prediction errors compared with those induced by initial errors alone. In this case, the impact of parameter errors cannot be overlooked. In the present paper, the optimal combination of these two types of errors [i.e., conditional nonlinear optimal perturbation （CNOP） errors] is calculated to investigate whether this optimal error combination may cause a more notable SPB phenomenon than that caused by initial errors alone. Using the CNOP approach, the CNOP errors and CNOP-I errors （optimal errors when only initial errors are considered） are calculated and then three aspects of error growth are compared： （1） the tendency of the seasonal error growth; （2） the prediction error of the sea surface temperature anomaly; and （3） the pattern of error growth. All three aspects show that the CNOP errors do not cause a more significant SPB than the CNOP-I errors. Therefore, this result suggests that we could improve the prediction of the E1 Nifio during spring by simply focusing on reducing the initial errors in this model.
文摘This paper investigated the spelling errors made by university students in Hong Kong.By analyzing the spelling errors in the untimed essays and exam scripts,we found that students are prone to make more spelling mistakes in exam scripts,the same type of errors occur in both of the two kinds of texts;and their ranks of the frequency also are the same.
文摘Based on the questionnaire, this study found that :1) Elementary learners were inclined to commit more global errors compared to their local errors, whilst advanced learners make more local errors; 2) Interlingual factors were more influential than intralingual factors in elementary learners' error making, but for advanced learners, intralingual factors played relatively a much more important role in error making; 3) Elementary learners preferred explicit correction whilst advanced learners favoured im?plicit correction in question-asking.
文摘On the basis of the theories of psycholinguistic perspective in language teaching and communicative approach in language learning,the author of this paper analysed briefly some tangible errors for the Chinese students in their reading comprehension in line with his own teaching experiences. The aim of the paper is to overcome the obstacles existing between the author’ s text writers and the text readers and to enable the latter to become effective readers.
基金The National Natural Science Foundation of China(No.61273236)the Natural Science Foundation of Jiangsu Province(No.BK2010239)the Ph.D.Programs Foundation of Ministry of Education of China(No.200802861061)
文摘This paper presents a novel approach to identify and correct the gross errors in the microelectromechanical system （MEMS） gyroscope used in ground vehicles by means of time series analysis. According to the characteristics of autocorrelation function （ACF） and partial autocorrelation function （PACF）, an autoregressive integrated moving average （ARIMA） model is roughly constructed. The rough model is optimized by combining with Akaike＇s information criterion （A/C）, and the parameters are estimated based on the least squares algorithm. After validation testing, the model is utilized to forecast the next output on the basis of the previous measurement. When the difference between the measurement and its prediction exceeds the defined threshold, the measurement is identified as a gross error and remedied by its prediction. A case study on the yaw rate is performed to illustrate the developed algorithm. Experimental results demonstrate that the proposed approach can effectively distinguish gross errors and make some reasonable remedies.
基金National Natural Science Foundation of China(No.61273172)
文摘This paper proposes a steady-state errors correction(SSEC)method for eliminating measurement errors.This method is based on the detections of error signal E(s)and output C(s)which generate an expected output R(s).In comparison with the conventional solutions which are based on detecting the expected output R(s)and output C(s)to obtain error signal E(s),the measurement errors are eliminated even the error might be at a significant level.Moreover,it is possible that the individual debugging by regulating the coefficient K for every member of the multiple objectives achieves the optimization of the open loop gain.Therefore,this simple method can be applied to the weak coupling and multiple objectives system,which is usually controlled by complex controller.The principle of eliminating measurement errors is derived analytically,and the advantages comparing with the conventional solutions are depicted.Based on the SSEC method analysis,an application of this method for an active power filter(APF)is investigated and the effectiveness and viability of the scheme are demonstrated through the simulation and experimental verifications.
文摘Before cognitive approach came into being in the 1960s, errors in L2 learning were always regarded as signs of failure which needed immediate attention from the teacher. By analyzing a student＇s writing, this paper tries to elaborate on the roles that errors can play in L2 learning process.
文摘The research on the common errors in junior English writings reflects the categories of errors, resources of errors, and how to do with errors in effective ways. Errors are divided into two types: intralingual errors and interlingual errors. The research finds that Chinese junior students depend heavily on their native language in English writing and finds out some effective strate gies avoiding errors in writing.
文摘This paper analyzes the lexical errors that students make in their written work.The errors are classified,and their causes are traced.The implications of the analysis are also provided in the paper.
文摘The software Wordsmith has been commonly used in corpus linguistics.In this paper,the author used the tool of Concord in Wordsmith to analyze various errors made by a student.Five passages made by the students are used.After annotating on the errors,the author uses Concord to sort out each error maker and made classification chart of the errors.All the errors are classified into two categories:errors caused by carelessness and by language ability.After analyzing,there are mainly three kinds of errors and in the first category and five kinds of errors in the second category.
基金National Natural Science Foundation of China (50475148)Aeronautical Science Foundation of China (04C53015)Areonautical Sci-tech Innovation Foundation of China (07B53004)
文摘This paper proposes a new approach to design pinion machine tool-settings for spiral bevel gears by controlling contact path and transmission errors. It is based on the satisfaction of contact condition of three given control points on the tooth surface. The three meshing points are controlled to be on a predesigned straight contact path that meets the pre-designed parabolic function of transmission errors. Designed separately, the magnitude of transmission errors and the orientation of the contact path are subjected to precise control. In addition, in order to meet the manufacturing requirements, we suggest to modify the values of blank offset, one of the pinion machine tool-settings, and redesign pinion ma- chine tool-settings to ensure that the magnitude and the geometry of transmission errors should not be influenced apart from minor effects on the predesigned straight contact path. The proposed approach together with its ideas has been proven by a numerical example and the manufacturing practice of a pair of spiral bevel gears.
