The aim of this study was to assess the potential of surgical guides as a complementary tool to augmented reality(AR)in enhancing the safety and precision of pedicle screw placement in spinal surgery.Four trainers wer...The aim of this study was to assess the potential of surgical guides as a complementary tool to augmented reality(AR)in enhancing the safety and precision of pedicle screw placement in spinal surgery.Four trainers were divided into the AR navigation group using surgical guides and the free-hand group.Each group consisted of a novice and an experienced spine surgeon.A total of 80 pedicle screws were implanted.First,the AR group reconstructed the 3D model and planned the screw insertion route according to the computed tomography data of L2 lumbar vertebrae.Then,the Microsoft HoloLens™2 was used to identify the vertebral model,and the planned virtual path was superimposed on the real cone model.Next,the screw was placed according to the projected trajectory.Finally,Micron Tracker was used to measure the deviation of screws from the preoperatively planned trajectory,and pedicle screws were evaluated using the Gertzbein-Robbins scale.In the AR group,the linear deviations of the experienced doctor and the novice were(1.59±0.39)mm and(1.73±0.52)mm respectively,and the angle deviations were 2.72°±0.61°and 2.87°±0.63°respectively.In the free-hand group,the linear deviations of the experienced doctor and the novice were(2.88±0.58)mm and(5.25±0.62)mm respectively,and the angle deviations were 4.41°±1.18°and 7.15°±1.45°respectively.Both kinds of deviations between the two groups were significantly different(P<0.05).The screw accuracy rate was 95%in the AR navigation group and 77.5%in the free-hand group.The results of this study indicate that the integration of surgical guides and AR is an innovative technique that can substantially enhance the safety and precision of spinal surgery and assist inexperienced doctors in completing the surgery.展开更多
BACKGROUND Acetabular component positioning in total hip arthroplasty(THA)is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications.The majority of acetabular compon...BACKGROUND Acetabular component positioning in total hip arthroplasty(THA)is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications.The majority of acetabular components are aligned freehand,without the use of navigation methods.Patient specific instruments(PSI)and three-dimensional(3D)printing of THA placement guides are increasingly used in primary THA to ensure optimal positioning.AIM To summarize the literature on 3D printing in THA and how they improve acetabular component alignment.METHODS PubMed was used to identify and access scientific studies reporting on different 3D printing methods used in THA.Eight studies with 236 hips in 228 patients were included.The studies could be divided into two main categories;3D printed models and 3D printed guides.RESULTS 3D printing in THA helped improve preoperative cup size planning and post-operative Harris hip scores between intervention and control groups(P=0.019,P=0.009).Otherwise,outcome measures were heterogeneous and thus difficult to compare.The overarching consensus between the studies is that the use of 3D guidance tools can assist in improving THA cup positioning and reduce the need for revision THA and the associated costs.CONCLUSION The implementation of 3D printing and PSI for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning.展开更多
The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load, and this kind of hydrostatic guide is usually applied to the machine tools with ...The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load, and this kind of hydrostatic guide is usually applied to the machine tools with moderate load. The static and dynamic characteristics of the guide have been studied by using some theoretical, numerical and experimental approaches, and some methods and measures have been proposed to improve its performances. The hydrostatic guide based on progressive mengen（PM） flow controller is especially suitable for the heavy numerical control（NC） machine tools. However, few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported. In this paper, the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing. On the basis of the analysis of hydrostatic bearing with circular pocket, some equations are derived for solving the static pressure, volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket. The function and the influencing factors of three pressures are clarified. The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived. With the help of software MATLAB, programs are coded with C＋＋ language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller. The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide, and it should be reduced as small as possible when the field working condition is met. Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides. The research work has instructing significance for analyzing and designing the guide with PM flow controller.展开更多
AIM: To present the radiological results of total knee arthroplasty(TKA) with use of patient specific matched guides(PSG) from different manufacturer in patients suffering from severe osteoarthritis of the knee joint....AIM: To present the radiological results of total knee arthroplasty(TKA) with use of patient specific matched guides(PSG) from different manufacturer in patients suffering from severe osteoarthritis of the knee joint.METHODS: This study describes the results of 57 knees operated with 4 different PSG systems and a group operated with conventional instrumentation(n = 60) by a single surgeon. The PSG systems were compared with each other and subdivided into cut- and pin PSG. The biomechanical axis [hip-knee-ankle angle(HKA)], varus/valgus of the femur [frontal femoral component(FFC)] and tibia(frontal tibial component) component, flexion/extension of the femur [flexion/extension of the femur component(LFC)] and posterior slope of the tibia [lateral tibial component(LTC)] component were evaluated on long-leg standing and lateral X-rays. A percentage of > 3° deviation was seen as an outlier. RESULTS: The inter class correlation coefficient(ICC) revealed that radiographic measurements between both assessors were reliable(ICC > 0.8). Fisher exact test was used to test differences of proportions. The percentage of outliers of the HKA-axis was comparable between both the PSG and conventional groups(12.28% vs 18.33%, P < 0.424) and the cut- and pin PSG groups(14.3% vs 10.3%, P < 1.00). The percentage of outliers of the FFC(0% vs 18.33%, P < 0.000), LFC(15.78% vs 58.33%, P < 0.000) and LTC(15.78% vs 41.67%, P < 0.033) were significant different in favour of the PSGgroup. There were no significant differences regarding the outliers between the individual PSG systems and the PSG group subdivided into cut- and pin PSG.CONCLUSION: PSG for TKA show significant less outliers compared to the conventional technique. These single surgeon results suggest that PSG are ready for primetime.展开更多
It was hypothesized that mesenchymal stem cells(MSCs) could provide necessary trophic factors when seeded onto the surfaces of commonly used nerve graft substitutes. We aimed to determine the gene expression of MSCs w...It was hypothesized that mesenchymal stem cells(MSCs) could provide necessary trophic factors when seeded onto the surfaces of commonly used nerve graft substitutes. We aimed to determine the gene expression of MSCs when influenced by Avance■ Nerve Grafts or Neura Gen■ Nerve Guides. Human adipose-derived MSCs were cultured and dynamically seeded onto 30 Avance■ Nerve Grafts and 30 Neura Gen■ Nerve Guides for 12 hours. At six time points after seeding, quantitative polymerase chain reaction analyses were performed for five samples per group. Neurotrophic [nerve growth factor(NGF), glial cell line-derived neurotrophic factor(GDNF), pleiotrophin(PTN), growth associated protein 43(GAP43) and brain-derived neurotrophic factor(BDNF)], myelination [peripheral myelin protein 22(PMP22) and myelin protein zero(MPZ)], angiogenic [platelet endothelial cell adhesion molecule 1(PECAM1/CD31) and vascular endothelial cell growth factor alpha(VEGFA)], extracellular matrix(ECM) [collagen type alpha I(COL1A1), collagen type alpha III(COL3A1), Fibulin 1(FBLN1) and laminin subunit beta 2(LAMB2)] and cell surface marker cluster of differentiation 96(CD96) gene expression was quantified. Unseeded Avance■ Nerve Grafts and Neura Gen■ Nerve Guides were used to evaluate the baseline gene expression, and unseeded MSCs provided the baseline gene expression of MSCs. The interaction of MSCs with the Avance■ Nerve Grafts led to a short-term upregulation of neurotrophic(NGF, GDNF and BDNF), myelination(PMP22 and MPZ) and angiogenic genes(CD31 and VEGFA) and a long-term upregulation of BDNF, VEGFA and COL1A1. The interaction between MSCs and the Neura Gen■ Nerve Guide led to short term upregulation of neurotrophic(NGF, GDNF and BDNF) myelination(PMP22 and MPZ), angiogenic(CD31 and VEGFA), ECM(COL1A1) and cell surface(CD96) genes and long-term upregulation of neurotrophic(GDNF and BDNF), angiogenic(CD31 and VEGFA), ECM genes(COL1A1, COL3A1, and FBLN1) and cell surface(CD96) genes. Analysis demonstrated MSCs seeded onto Neura Gen■ Nerve Guides expressed significantly higher levels of neurotrophic(PTN), angiogenic(VEGFA) and ECM(COL3A1, FBLN1) genes in the long term period compared to MSCs seeded onto Avance■ Nerve Grafts. Overall, the interaction between human MSCs and both nerve graft substitutes resulted in a significant upregulation of the expression of numerous genes important for nerve regeneration over time. The in vitro interaction of MSCs with the Neura Gen■ Nerve Guide was more pronounced, particularly in the long term period(> 14 days after seeding). These results suggest that MSC-seeding has potential to be applied in a clinical setting, which needs to be confirmed in future in vitro and in vivo research.展开更多
A teaching model based on constructivism is proposed in this paper. The model contains five teaching steps, e.g. interpretation teaching, questioning- dialogue, knowledge and skills teaching, discussion- collaboration...A teaching model based on constructivism is proposed in this paper. The model contains five teaching steps, e.g. interpretation teaching, questioning- dialogue, knowledge and skills teaching, discussion- collaboration and field training. Practice proves that it can effectively improve the training efficiency of the training of English guides of stone inscription relics and enhance their interpretation quality and English skills.展开更多
This paper gives the simple and logical approach of LP modes in circular and elliptical waveguides. Earlier the basic approach of modes in circular and elliptical fibers was studied by the authors. In this paper, the ...This paper gives the simple and logical approach of LP modes in circular and elliptical waveguides. Earlier the basic approach of modes in circular and elliptical fibers was studied by the authors. In this paper, the role of radial antinode in circular and elliptical waveguides is given clearly. Splitting of modes in circular and elliptical fiber has been discussed.展开更多
Ubiquitous computing plays an increasing role in our lives. Typically, applications in ubiquitous computing environ-ments are context aware, namely, they react to the situations of their users at a given moment in tim...Ubiquitous computing plays an increasing role in our lives. Typically, applications in ubiquitous computing environ-ments are context aware, namely, they react to the situations of their users at a given moment in time. One example for such environment is visitor’s guides in cultural heritage sites, supporting visits of individuals or small groups, such as families or friends. In such environments, it is well known that interaction among visitors enhances the overall visit experience. Recently, some research prototypes of visitor’s guides have started supporting such interaction through textual communication services embedded in them. However, these applications have so far been developed separately in an ad-hoc manner, despite common features and infrastructures they share. The research described here generalizes communication services offered by different visitor’s guides and suggests a systematic and generic framework for developing context-aware communication services for visitor’s guides. The specific communication services are abstracted into a domain model, later used in practice for adapting and tailoring the different concepts to the specific requirements of the applications. The framework is demonstrated in the specific setting of a multi-agent museum visitor’s guide system. We also show that the suggested framework is not limited to the specific museum visitor’s guide system but may facilitate the development of context-aware communication applications in general.展开更多
As we know, PACT (President's Advisory Committee on Future Technology) members of the IEC (International Electrotechnical Commission) used to be CTOs of large companies from only a few developed countries such as ...As we know, PACT (President's Advisory Committee on Future Technology) members of the IEC (International Electrotechnical Commission) used to be CTOs of large companies from only a few developed countries such as the United States, Germany and Japan. However, Haier Group has broken the ice since it entered the IEC/PACT commission in June 2005, lifting the curtain on international standardization of our national enterprises. And now, Haier is hosting the IEC/PACT annual conference in November 2007. Could you introduce it in detail?展开更多
Travel guides are not only important windows for foreign visitors to obtain information on China's scenic spots, but also main mediums for spreading Chinese culture. By comparing and analyzing the differences betw...Travel guides are not only important windows for foreign visitors to obtain information on China's scenic spots, but also main mediums for spreading Chinese culture. By comparing and analyzing the differences between Chinese and English travel guides, this paper, combined with the case of Henan scenic spots, makes a study of the translation principle, translation strategy and translation methods of travel guides from the perspective of Skopostheory.展开更多
The dependences of light efficiency of radiation （LER） and color-rendering index （CRI） of trichromatic white light-emitting diode （wLED）, composed of blue LED die, green/yellow, and red phosphors, on the peak wa...The dependences of light efficiency of radiation （LER） and color-rendering index （CRI） of trichromatic white light-emitting diode （wLED）, composed of blue LED die, green/yellow, and red phosphors, on the peak wave- length of each primary were investigated by theoretical calculations, at correlative color temperature （CCT） from 2,700 to 6,500 K. The peak wavelength of InGaN based blue LED chip ranges from 450 to 471 nm, while those of Ca3Sc2Si3012：Ce3＋, b-SiA1ON：Eu2＋, and Y3A15012：Ce3＋ based green/yellow phosphors range from 511 to 572 nm, and those of Sr2SisN8：Eu2＋ and CaA1SiN3：Eu2＋ red phosphors range from 620 to 650 nm, which cover almost all the practically used, commercially available wave bands until now. Then, based on the results, selection guides of peak wavelengths for blue LED chip and phosphors to obtain tradeoff LER 〉280 lm.W-1 as well as CRI 〉80 in all CCTs are proposed. The favorable wave bands of each primary are suggested.展开更多
Plasmonic waveguides,as a competitive candidate,have been widely studied in rapid developing photonic integrated circuits(PICs)and optical interconnection fields.However,crosstalk between plasmonic waveguides is a cri...Plasmonic waveguides,as a competitive candidate,have been widely studied in rapid developing photonic integrated circuits(PICs)and optical interconnection fields.However,crosstalk between plasmonic waveguides is a critical issue that has to be considered in practice.Actually,crosstalk dominates the ultimate integration density of the planar photonic circuits.This paper reviews the recent research work on evaluation methods and crosstalk suppression approaches of plasmonic waveguides.Three crosstalk evaluation methods based on comparison of specific parameters of waveguides have been summarized.Furthermore,four specific approaches to reduce crosstalk have been illustrated as two categories according to their impacts on waveguide performances and the whole circuit.One means of crosstalk suppression is changing the placement of waveguides,which could maintain the transmission characteristics of the original waveguide.The other means is inserting medium,which has the advantage of occupying smaller space compared to the first method.Consequently,to suppress crosstalk between plasmonic waveguides,one should choose suitable approach.展开更多
Tourist guides as front-line professionals, information-givers, and interpreters act as destination representatives and ＂ambassadors＂ in the eyes of tourists （Raboti6, 2010）. This paper, using an empirical analysi...Tourist guides as front-line professionals, information-givers, and interpreters act as destination representatives and ＂ambassadors＂ in the eyes of tourists （Raboti6, 2010）. This paper, using an empirical analysis of coach tour foreign tourists travelling in Portugal, intends to determine how tourist destination image （TDI） is modified and enhanced through the influence of tourist guide performance and tourist satisfaction with the guided tour. A survey questionnaire of first-time package tour travellers to Portugal revealed a positive change in attitude to image components such as monuments/museums, tourist information, landscape, and gastronomy and wines, confirming that the tourist guide＇s attributes in communication skills and scholar knowledge （history, art, and popular culture） together with highly rated tourist satisfaction with the guided tour concerning the professional competence of a bus driver were critical in enhancing Portugal destination image. Marketing implications for senior coach tour in Portugal are drawn.展开更多
It is important for a completive tourism destination to ensure that tourists get the company of a professional tour guide who guides and interprets attraction in the areas visited. Undefined level of education, lack o...It is important for a completive tourism destination to ensure that tourists get the company of a professional tour guide who guides and interprets attraction in the areas visited. Undefined level of education, lack of standardized training curriculum, and lack of barrier to the guiding career have affected the performance of tour guides in Kenya. Limited research in Kenya has been conducted to establish the role of guides in satisfying customer and protecting the environment. The study objective was to examine tour guides＇ interpretation knowledge and their opinion on areas that require more training so as to improve their performance. The study hypothesized that tour guides＇ opinions on their training needs are independent on the level of education, work experience and qualification. It is hypothesized that guides require additional training in flora and fauna of East Africa, cultural heritage and customer service. They require training in ICT （Information Communications Technology）, eco-tourism principles, and at least one foreign language. The study hypothesizes that the higher the level of a guide＇s training, the more resourceful the guide will be. The study used qualitative and quantitative research approaches where questionnaires, interviews and focus groups discussion （FGDs） were used to collect the primary data. The finding shows that tour guides＇ opinions on areas they require further training were independent of their highest level of education, work experience and qualification. Most guides irrespective of their level of education, work experience and qualifications were of the opinion that they needed more training on mammals and plants （χ^2 = 1.07, df= 2, P = 0.583）, training on birds and insects （χ^2 = 0.254, df= 2, P = 0.885） and training on culture and history of East Africa （χ^2 = 1.140, df= 2, P = 0.566）. Respondents＇ training needs were independent on the duration of tour guiding course training had taken. Guides trained for less than six months, one year and more than two years agreed that training on foreign language （χ^2 = 4.84, df = 2, P = 0.196）, ecotourism principles （χ^2 = 1.62, df = 2, P = 0.653） and tour planning and costing （χ^2 = 399, df = 3, P = 0.262） would improve their performance. The study concludes that tour guides are aware of the areas that they need to be trained and should be consulted before organizing such training. They require more training irrespective of their level of education, certification and work experience. The study recommends tour guide curriculum be standardized and all guides should sit for an exam before they are licensed to guide and only those with such license be allowed to practice guiding.展开更多
We investigate the guided modes in monolayer graphene-based waveguides with asymmetric quantum well structure induced by unequal dc voltages. The dispersion relation for the guided modes is obtained analytically, the ...We investigate the guided modes in monolayer graphene-based waveguides with asymmetric quantum well structure induced by unequal dc voltages. The dispersion relation for the guided modes is obtained analytically, the structures of the guided modes are discussed under three distinct cases. For the cases of the classical motion and the Klein tunneling, the asymmetric structure does not influence the mode structures dramatically compared with that in the symmetric waveguide. But for the mixing case of the former two, the mode structures and the motion characteristics for the electron and the hole exhibit different behaviors at same condition. The results may be helpful for the practical application of graphene-based quantum devices.展开更多
The broadband fluorescence guided-waves excited in DANS/PMMA polymer thin film waveguides by an Ar+laser beam were demonstrated in terms of the observation of mlines with colour array.Considering the high brightness o...The broadband fluorescence guided-waves excited in DANS/PMMA polymer thin film waveguides by an Ar+laser beam were demonstrated in terms of the observation of mlines with colour array.Considering the high brightness of these m-lines observation,we assert that it is a kind of stimulated amplification of fluorescence guided-wave.展开更多
For the virtual environment (VE) to control remote robots through Internet, this paper proposes an operational idea based on virtual guides (VGs). The VGs consist of three types, line VG, plane VG, and body VG, which ...For the virtual environment (VE) to control remote robots through Internet, this paper proposes an operational idea based on virtual guides (VGs). The VGs consist of three types, line VG, plane VG, and body VG, which can greatly enhance the safety and flexibility of the man-machine system. Through the analysis of several common cases, the idea of the VGs are first introduced and described. Second, detailed descriptions of the three VGs are given, and then a uniform representation of all VGs is given. Finally, a typical experiment is designed and implemented according to the modes of video feedback, video&VE feedback, and video&VE&VG feedback. Experimental results show that the operation based on VEs and VGs have significant advantages over that based on video feedback, and VGs can greatly improve the ability of the VE to control remote robots, thus obtaining high and efficient man-machine cooperation.展开更多
The effects of the location,number and stiffness of guide pads on the lowest critical rotational frequencies of the rotating circular saw damped at the inside and free at the perimeter are discussed by the non linear...The effects of the location,number and stiffness of guide pads on the lowest critical rotational frequencies of the rotating circular saw damped at the inside and free at the perimeter are discussed by the non linear theory and the perturbation theory of structural vibration analysis The influence of the centrifugal force and the cutting temperature are considered in the course of the analysis The results of the analysis and the calculation show that the introduction of one guide does not stably raise critical rotational frequencies of the circular saw The two guides can raise lowest critical rotational frequency of the circular saw when the angle between the two guides fixed on the direction of the circumference satisfies the certain conditions展开更多
Multilayer cladded slab waveguides have been solved by using asymptotic theory once or twice. Based on the solution of a three layer slab waveguide, the wave number of guided modes has been expanded in series of one o...Multilayer cladded slab waveguides have been solved by using asymptotic theory once or twice. Based on the solution of a three layer slab waveguide, the wave number of guided modes has been expanded in series of one or two small parameters. One side cladded slab, two side cladded slab and two parallel cladded slab waveguide system are demonstrated to show how to use this essentially analytic method. Numerical examples have also been given and compared with exact solutions, eved the first or second order solutions are highly accurate.展开更多
基金the National Natural Science Foundation of China(No.11502146)the 1 Batch of 2021 MOE of PRC Industry University Collaborative Education Program(No.202101042008)。
文摘The aim of this study was to assess the potential of surgical guides as a complementary tool to augmented reality(AR)in enhancing the safety and precision of pedicle screw placement in spinal surgery.Four trainers were divided into the AR navigation group using surgical guides and the free-hand group.Each group consisted of a novice and an experienced spine surgeon.A total of 80 pedicle screws were implanted.First,the AR group reconstructed the 3D model and planned the screw insertion route according to the computed tomography data of L2 lumbar vertebrae.Then,the Microsoft HoloLens™2 was used to identify the vertebral model,and the planned virtual path was superimposed on the real cone model.Next,the screw was placed according to the projected trajectory.Finally,Micron Tracker was used to measure the deviation of screws from the preoperatively planned trajectory,and pedicle screws were evaluated using the Gertzbein-Robbins scale.In the AR group,the linear deviations of the experienced doctor and the novice were(1.59±0.39)mm and(1.73±0.52)mm respectively,and the angle deviations were 2.72°±0.61°and 2.87°±0.63°respectively.In the free-hand group,the linear deviations of the experienced doctor and the novice were(2.88±0.58)mm and(5.25±0.62)mm respectively,and the angle deviations were 4.41°±1.18°and 7.15°±1.45°respectively.Both kinds of deviations between the two groups were significantly different(P<0.05).The screw accuracy rate was 95%in the AR navigation group and 77.5%in the free-hand group.The results of this study indicate that the integration of surgical guides and AR is an innovative technique that can substantially enhance the safety and precision of spinal surgery and assist inexperienced doctors in completing the surgery.
文摘BACKGROUND Acetabular component positioning in total hip arthroplasty(THA)is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications.The majority of acetabular components are aligned freehand,without the use of navigation methods.Patient specific instruments(PSI)and three-dimensional(3D)printing of THA placement guides are increasingly used in primary THA to ensure optimal positioning.AIM To summarize the literature on 3D printing in THA and how they improve acetabular component alignment.METHODS PubMed was used to identify and access scientific studies reporting on different 3D printing methods used in THA.Eight studies with 236 hips in 228 patients were included.The studies could be divided into two main categories;3D printed models and 3D printed guides.RESULTS 3D printing in THA helped improve preoperative cup size planning and post-operative Harris hip scores between intervention and control groups(P=0.019,P=0.009).Otherwise,outcome measures were heterogeneous and thus difficult to compare.The overarching consensus between the studies is that the use of 3D guidance tools can assist in improving THA cup positioning and reduce the need for revision THA and the associated costs.CONCLUSION The implementation of 3D printing and PSI for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning.
文摘The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load, and this kind of hydrostatic guide is usually applied to the machine tools with moderate load. The static and dynamic characteristics of the guide have been studied by using some theoretical, numerical and experimental approaches, and some methods and measures have been proposed to improve its performances. The hydrostatic guide based on progressive mengen（PM） flow controller is especially suitable for the heavy numerical control（NC） machine tools. However, few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported. In this paper, the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing. On the basis of the analysis of hydrostatic bearing with circular pocket, some equations are derived for solving the static pressure, volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket. The function and the influencing factors of three pressures are clarified. The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived. With the help of software MATLAB, programs are coded with C＋＋ language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller. The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide, and it should be reduced as small as possible when the field working condition is met. Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides. The research work has instructing significance for analyzing and designing the guide with PM flow controller.
文摘AIM: To present the radiological results of total knee arthroplasty(TKA) with use of patient specific matched guides(PSG) from different manufacturer in patients suffering from severe osteoarthritis of the knee joint.METHODS: This study describes the results of 57 knees operated with 4 different PSG systems and a group operated with conventional instrumentation(n = 60) by a single surgeon. The PSG systems were compared with each other and subdivided into cut- and pin PSG. The biomechanical axis [hip-knee-ankle angle(HKA)], varus/valgus of the femur [frontal femoral component(FFC)] and tibia(frontal tibial component) component, flexion/extension of the femur [flexion/extension of the femur component(LFC)] and posterior slope of the tibia [lateral tibial component(LTC)] component were evaluated on long-leg standing and lateral X-rays. A percentage of > 3° deviation was seen as an outlier. RESULTS: The inter class correlation coefficient(ICC) revealed that radiographic measurements between both assessors were reliable(ICC > 0.8). Fisher exact test was used to test differences of proportions. The percentage of outliers of the HKA-axis was comparable between both the PSG and conventional groups(12.28% vs 18.33%, P < 0.424) and the cut- and pin PSG groups(14.3% vs 10.3%, P < 1.00). The percentage of outliers of the FFC(0% vs 18.33%, P < 0.000), LFC(15.78% vs 58.33%, P < 0.000) and LTC(15.78% vs 41.67%, P < 0.033) were significant different in favour of the PSGgroup. There were no significant differences regarding the outliers between the individual PSG systems and the PSG group subdivided into cut- and pin PSG.CONCLUSION: PSG for TKA show significant less outliers compared to the conventional technique. These single surgeon results suggest that PSG are ready for primetime.
基金supported by the National Institute of Neurological Disorders and Stroke of the National Institutes of Health (No. R01NS102360)。
文摘It was hypothesized that mesenchymal stem cells(MSCs) could provide necessary trophic factors when seeded onto the surfaces of commonly used nerve graft substitutes. We aimed to determine the gene expression of MSCs when influenced by Avance■ Nerve Grafts or Neura Gen■ Nerve Guides. Human adipose-derived MSCs were cultured and dynamically seeded onto 30 Avance■ Nerve Grafts and 30 Neura Gen■ Nerve Guides for 12 hours. At six time points after seeding, quantitative polymerase chain reaction analyses were performed for five samples per group. Neurotrophic [nerve growth factor(NGF), glial cell line-derived neurotrophic factor(GDNF), pleiotrophin(PTN), growth associated protein 43(GAP43) and brain-derived neurotrophic factor(BDNF)], myelination [peripheral myelin protein 22(PMP22) and myelin protein zero(MPZ)], angiogenic [platelet endothelial cell adhesion molecule 1(PECAM1/CD31) and vascular endothelial cell growth factor alpha(VEGFA)], extracellular matrix(ECM) [collagen type alpha I(COL1A1), collagen type alpha III(COL3A1), Fibulin 1(FBLN1) and laminin subunit beta 2(LAMB2)] and cell surface marker cluster of differentiation 96(CD96) gene expression was quantified. Unseeded Avance■ Nerve Grafts and Neura Gen■ Nerve Guides were used to evaluate the baseline gene expression, and unseeded MSCs provided the baseline gene expression of MSCs. The interaction of MSCs with the Avance■ Nerve Grafts led to a short-term upregulation of neurotrophic(NGF, GDNF and BDNF), myelination(PMP22 and MPZ) and angiogenic genes(CD31 and VEGFA) and a long-term upregulation of BDNF, VEGFA and COL1A1. The interaction between MSCs and the Neura Gen■ Nerve Guide led to short term upregulation of neurotrophic(NGF, GDNF and BDNF) myelination(PMP22 and MPZ), angiogenic(CD31 and VEGFA), ECM(COL1A1) and cell surface(CD96) genes and long-term upregulation of neurotrophic(GDNF and BDNF), angiogenic(CD31 and VEGFA), ECM genes(COL1A1, COL3A1, and FBLN1) and cell surface(CD96) genes. Analysis demonstrated MSCs seeded onto Neura Gen■ Nerve Guides expressed significantly higher levels of neurotrophic(PTN), angiogenic(VEGFA) and ECM(COL3A1, FBLN1) genes in the long term period compared to MSCs seeded onto Avance■ Nerve Grafts. Overall, the interaction between human MSCs and both nerve graft substitutes resulted in a significant upregulation of the expression of numerous genes important for nerve regeneration over time. The in vitro interaction of MSCs with the Neura Gen■ Nerve Guide was more pronounced, particularly in the long term period(> 14 days after seeding). These results suggest that MSC-seeding has potential to be applied in a clinical setting, which needs to be confirmed in future in vitro and in vivo research.
文摘A teaching model based on constructivism is proposed in this paper. The model contains five teaching steps, e.g. interpretation teaching, questioning- dialogue, knowledge and skills teaching, discussion- collaboration and field training. Practice proves that it can effectively improve the training efficiency of the training of English guides of stone inscription relics and enhance their interpretation quality and English skills.
文摘This paper gives the simple and logical approach of LP modes in circular and elliptical waveguides. Earlier the basic approach of modes in circular and elliptical fibers was studied by the authors. In this paper, the role of radial antinode in circular and elliptical waveguides is given clearly. Splitting of modes in circular and elliptical fiber has been discussed.
文摘Ubiquitous computing plays an increasing role in our lives. Typically, applications in ubiquitous computing environ-ments are context aware, namely, they react to the situations of their users at a given moment in time. One example for such environment is visitor’s guides in cultural heritage sites, supporting visits of individuals or small groups, such as families or friends. In such environments, it is well known that interaction among visitors enhances the overall visit experience. Recently, some research prototypes of visitor’s guides have started supporting such interaction through textual communication services embedded in them. However, these applications have so far been developed separately in an ad-hoc manner, despite common features and infrastructures they share. The research described here generalizes communication services offered by different visitor’s guides and suggests a systematic and generic framework for developing context-aware communication services for visitor’s guides. The specific communication services are abstracted into a domain model, later used in practice for adapting and tailoring the different concepts to the specific requirements of the applications. The framework is demonstrated in the specific setting of a multi-agent museum visitor’s guide system. We also show that the suggested framework is not limited to the specific museum visitor’s guide system but may facilitate the development of context-aware communication applications in general.
文摘As we know, PACT (President's Advisory Committee on Future Technology) members of the IEC (International Electrotechnical Commission) used to be CTOs of large companies from only a few developed countries such as the United States, Germany and Japan. However, Haier Group has broken the ice since it entered the IEC/PACT commission in June 2005, lifting the curtain on international standardization of our national enterprises. And now, Haier is hosting the IEC/PACT annual conference in November 2007. Could you introduce it in detail?
文摘Travel guides are not only important windows for foreign visitors to obtain information on China's scenic spots, but also main mediums for spreading Chinese culture. By comparing and analyzing the differences between Chinese and English travel guides, this paper, combined with the case of Henan scenic spots, makes a study of the translation principle, translation strategy and translation methods of travel guides from the perspective of Skopostheory.
基金financially supported by the National Natural Science Foundation of China(No.51272027)
文摘The dependences of light efficiency of radiation （LER） and color-rendering index （CRI） of trichromatic white light-emitting diode （wLED）, composed of blue LED die, green/yellow, and red phosphors, on the peak wave- length of each primary were investigated by theoretical calculations, at correlative color temperature （CCT） from 2,700 to 6,500 K. The peak wavelength of InGaN based blue LED chip ranges from 450 to 471 nm, while those of Ca3Sc2Si3012：Ce3＋, b-SiA1ON：Eu2＋, and Y3A15012：Ce3＋ based green/yellow phosphors range from 511 to 572 nm, and those of Sr2SisN8：Eu2＋ and CaA1SiN3：Eu2＋ red phosphors range from 620 to 650 nm, which cover almost all the practically used, commercially available wave bands until now. Then, based on the results, selection guides of peak wavelengths for blue LED chip and phosphors to obtain tradeoff LER 〉280 lm.W-1 as well as CRI 〉80 in all CCTs are proposed. The favorable wave bands of each primary are suggested.
文摘Plasmonic waveguides,as a competitive candidate,have been widely studied in rapid developing photonic integrated circuits(PICs)and optical interconnection fields.However,crosstalk between plasmonic waveguides is a critical issue that has to be considered in practice.Actually,crosstalk dominates the ultimate integration density of the planar photonic circuits.This paper reviews the recent research work on evaluation methods and crosstalk suppression approaches of plasmonic waveguides.Three crosstalk evaluation methods based on comparison of specific parameters of waveguides have been summarized.Furthermore,four specific approaches to reduce crosstalk have been illustrated as two categories according to their impacts on waveguide performances and the whole circuit.One means of crosstalk suppression is changing the placement of waveguides,which could maintain the transmission characteristics of the original waveguide.The other means is inserting medium,which has the advantage of occupying smaller space compared to the first method.Consequently,to suppress crosstalk between plasmonic waveguides,one should choose suitable approach.
文摘Tourist guides as front-line professionals, information-givers, and interpreters act as destination representatives and ＂ambassadors＂ in the eyes of tourists （Raboti6, 2010）. This paper, using an empirical analysis of coach tour foreign tourists travelling in Portugal, intends to determine how tourist destination image （TDI） is modified and enhanced through the influence of tourist guide performance and tourist satisfaction with the guided tour. A survey questionnaire of first-time package tour travellers to Portugal revealed a positive change in attitude to image components such as monuments/museums, tourist information, landscape, and gastronomy and wines, confirming that the tourist guide＇s attributes in communication skills and scholar knowledge （history, art, and popular culture） together with highly rated tourist satisfaction with the guided tour concerning the professional competence of a bus driver were critical in enhancing Portugal destination image. Marketing implications for senior coach tour in Portugal are drawn.
文摘It is important for a completive tourism destination to ensure that tourists get the company of a professional tour guide who guides and interprets attraction in the areas visited. Undefined level of education, lack of standardized training curriculum, and lack of barrier to the guiding career have affected the performance of tour guides in Kenya. Limited research in Kenya has been conducted to establish the role of guides in satisfying customer and protecting the environment. The study objective was to examine tour guides＇ interpretation knowledge and their opinion on areas that require more training so as to improve their performance. The study hypothesized that tour guides＇ opinions on their training needs are independent on the level of education, work experience and qualification. It is hypothesized that guides require additional training in flora and fauna of East Africa, cultural heritage and customer service. They require training in ICT （Information Communications Technology）, eco-tourism principles, and at least one foreign language. The study hypothesizes that the higher the level of a guide＇s training, the more resourceful the guide will be. The study used qualitative and quantitative research approaches where questionnaires, interviews and focus groups discussion （FGDs） were used to collect the primary data. The finding shows that tour guides＇ opinions on areas they require further training were independent of their highest level of education, work experience and qualification. Most guides irrespective of their level of education, work experience and qualifications were of the opinion that they needed more training on mammals and plants （χ^2 = 1.07, df= 2, P = 0.583）, training on birds and insects （χ^2 = 0.254, df= 2, P = 0.885） and training on culture and history of East Africa （χ^2 = 1.140, df= 2, P = 0.566）. Respondents＇ training needs were independent on the duration of tour guiding course training had taken. Guides trained for less than six months, one year and more than two years agreed that training on foreign language （χ^2 = 4.84, df = 2, P = 0.196）, ecotourism principles （χ^2 = 1.62, df = 2, P = 0.653） and tour planning and costing （χ^2 = 399, df = 3, P = 0.262） would improve their performance. The study concludes that tour guides are aware of the areas that they need to be trained and should be consulted before organizing such training. They require more training irrespective of their level of education, certification and work experience. The study recommends tour guide curriculum be standardized and all guides should sit for an exam before they are licensed to guide and only those with such license be allowed to practice guiding.
基金Supported by the Natural Science Foundation of China under Grant No.11204383the Fundamental Research Funds for the Central Universities of South-Central University for Nationalities under Grant No.CZQ11001+2 种基金the Natural Science Basic Research Plan in Shaanxi Province of China under Grant No.11JK0556the Scientific Research Program of Shaanxi Provincial Education Department under Grant No.2011JM1014the National Natural Science Foundation of Shaanxi University of Science and Technology under Grant No.ZX11-33
文摘We investigate the guided modes in monolayer graphene-based waveguides with asymmetric quantum well structure induced by unequal dc voltages. The dispersion relation for the guided modes is obtained analytically, the structures of the guided modes are discussed under three distinct cases. For the cases of the classical motion and the Klein tunneling, the asymmetric structure does not influence the mode structures dramatically compared with that in the symmetric waveguide. But for the mixing case of the former two, the mode structures and the motion characteristics for the electron and the hole exhibit different behaviors at same condition. The results may be helpful for the practical application of graphene-based quantum devices.
基金the National Natural Science Foundation of China,and by the National 863 High-Tech.Bond of China.
文摘The broadband fluorescence guided-waves excited in DANS/PMMA polymer thin film waveguides by an Ar+laser beam were demonstrated in terms of the observation of mlines with colour array.Considering the high brightness of these m-lines observation,we assert that it is a kind of stimulated amplification of fluorescence guided-wave.
文摘For the virtual environment (VE) to control remote robots through Internet, this paper proposes an operational idea based on virtual guides (VGs). The VGs consist of three types, line VG, plane VG, and body VG, which can greatly enhance the safety and flexibility of the man-machine system. Through the analysis of several common cases, the idea of the VGs are first introduced and described. Second, detailed descriptions of the three VGs are given, and then a uniform representation of all VGs is given. Finally, a typical experiment is designed and implemented according to the modes of video feedback, video&VE feedback, and video&VE&VG feedback. Experimental results show that the operation based on VEs and VGs have significant advantages over that based on video feedback, and VGs can greatly improve the ability of the VE to control remote robots, thus obtaining high and efficient man-machine cooperation.
文摘The effects of the location,number and stiffness of guide pads on the lowest critical rotational frequencies of the rotating circular saw damped at the inside and free at the perimeter are discussed by the non linear theory and the perturbation theory of structural vibration analysis The influence of the centrifugal force and the cutting temperature are considered in the course of the analysis The results of the analysis and the calculation show that the introduction of one guide does not stably raise critical rotational frequencies of the circular saw The two guides can raise lowest critical rotational frequency of the circular saw when the angle between the two guides fixed on the direction of the circumference satisfies the certain conditions
文摘Multilayer cladded slab waveguides have been solved by using asymptotic theory once or twice. Based on the solution of a three layer slab waveguide, the wave number of guided modes has been expanded in series of one or two small parameters. One side cladded slab, two side cladded slab and two parallel cladded slab waveguide system are demonstrated to show how to use this essentially analytic method. Numerical examples have also been given and compared with exact solutions, eved the first or second order solutions are highly accurate.
