Every day we experience relationships with artefacts, which describe material objects made by humans in order to reach a goal and exploit the human feature to plan ahead. Artefacts bring together cognitive evolution a...Every day we experience relationships with artefacts, which describe material objects made by humans in order to reach a goal and exploit the human feature to plan ahead. Artefacts bring together cognitive evolution and technical enhancement. Although artefacts are conceived as technical, we are now facing a relationship with Information Technology （IT） artefacts. IT artefacts include both hardware and software, as a two-sided entity. The definition of IT artefact corresponds with the Saussurean linguistic sign： a two-sided entity constituted by the signifier （hardware） and the signified （software）. I claim that IT artefacts share this ontological trait with the linguistic sign. I will show that IT artefacts are the result of design and planning, while language--which is an institution--is not the fabrication of one human but linked to collective human activity.展开更多
In order to develop skin artefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone nlbber and knitted nylon sheet were selected to manufacture an artific...In order to develop skin artefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone nlbber and knitted nylon sheet were selected to manufacture an artificial skin, due to their higher elastic strain and high flexibility. Tensile and scissors cutting tests were conducted to characterise the matrix and reinforcing materials and the skin artefact. Material properties of the individual and the composite materials were compared with the measured properties of real octopus skin presented ill Part I. The Young＇s modulus of the skin should be below 20 MPa and the elastic strain range should be over 60%. The fracture toughness should be at least 0.9 kJ.m 2. Tubes made of the skin artefact filled with liquid were tested to study volume change under deformation. Finite element analysis model was developed to simulate the material and arm structure under tensile loading. Results show that the skin artefact developed has similar mechanical properties as the real octopus skin and satisfies all the design specifications of the OCTOPUS robot.展开更多
Cone beam computed tomography (CBCT) is the modern third dimension applied in the field of oral maxillofacial region. With lower radiation dose compared to conventional CT, its applications in dentistry has increased ...Cone beam computed tomography (CBCT) is the modern third dimension applied in the field of oral maxillofacial region. With lower radiation dose compared to conventional CT, its applications in dentistry has increased tremendously. Artefacts can seriously degrade the quality of computed tomographic (CBCT) images, sometimes to the point of making them diagnostically unusable. To optimize image quality, it is necessary to understand why artifacts occur and how they can be prevented or suppressed. CT artifacts originate from a range of sources;physical based, scanner based and patient based. This article highlights the causes of artefacts on CBCT images and methods to avoid them.展开更多
X-ray analyzer-based imaging(ABI) is a powerful phase-sensitive technique that can provide a wide dynamic range of density and extract useful physical properties of the sample. It derives contrast from x-ray absorptio...X-ray analyzer-based imaging(ABI) is a powerful phase-sensitive technique that can provide a wide dynamic range of density and extract useful physical properties of the sample. It derives contrast from x-ray absorption, refraction, and scattering properties of the investigated sample. However, x-ray ABI setups can be susceptible to external vibrations, and mechanical imprecisions of system components, e.g., the precision of motor, which are unavoidable in practical experiments. Those factors will provoke deviations of analyzer angular positions and hence errors in the acquired image data.Consequently, those errors will introduce artefacts in the retrieved refraction and scattering images. These artefacts are disadvantageous for further image interpretation and tomographic reconstruction. For this purpose, this work aims to analyze image artefacts resulting from deviations of analyzer angular positions. Analytical expressions of the refraction and scattering image artefacts are derived theoretically and validated by synchrotron radiation experiments. The results show that for the refraction image, the artefact is independent of the sample’s absorption and scattering signals. By contrast, artefact of the scattering image is dependent on both the sample’s refraction and scattering signals, but not on absorption signal.Furthermore, the effect of deviations of analyzer angular positions on the accuracy of the retrieved images is investigated,which can be of use for optimization of data acquisition. This work offers the possibility to develop advanced multi-contrast image retrieval algorithms that suppress artefacts in the retrieved refraction and scattering images in x-ray analyzer-based imaging.展开更多
Objective: To propose a new method of classifying film-screen radiographic artefacts. Methodology: A prospective study was carried out at the Radiology Department of a University Teaching Hospital in Nigeria between J...Objective: To propose a new method of classifying film-screen radiographic artefacts. Methodology: A prospective study was carried out at the Radiology Department of a University Teaching Hospital in Nigeria between June, 2011 and June 2013. Radiographs were assessed with the aid of a viewing box for artefacts which were arranged according to prior classifications by other researchers. They were subsequently grouped according to pre-arranged format into the new classification. Result: The following groups were observed: packaging (dark), procedure (greyscale), patient (greyscale), pre-processor (dark), processor (greyscale) and post-processor (greyscale). Conclusion: Classification of artefacts based on appearance and stage of introduction into film is easier to understand and remember.展开更多
Eight new Palaeolithic open-air sites were identified and 770 stone artefacts were collected from 2009 to 2011 in the Lantian area of the Bahe River valley, central China. Because the famous Homo erectus fossils were ...Eight new Palaeolithic open-air sites were identified and 770 stone artefacts were collected from 2009 to 2011 in the Lantian area of the Bahe River valley, central China. Because the famous Homo erectus fossils were unearthed at the Gongwangling and Chenjiawo localities, and more than 30 Palaeolithic open-air sites were investigated in the 1960s in this region, the catchment of Bahe River is regarded as one of the most important hominin sites from the late early Pleistocene to the middle Pleistocene. These eight newly discovered open-air sites are located at the second(n = 6), third(n = 1) or higher terraces(n = 1) of the Bahe River. The Diaozhai section on the second terrace was sampled in detail. Two samples were collected for optically stimulated luminescence dating(OSL). The OSL results suggest that a buried lithic artefact layer at the Diaozhai site spans approximately 70–30 ka. The lithic assemblage analysis suggests that the stone artefacts were made of local pebbles/cobbles such as greywacke, quartz, sandstone and igneous rocks. The main percussion techniques that were used were direct hard hammer percussion and bi-polar techniques. The lithic artefacts comprise hammer stones, cores, flakes, retouched tools and flaking debris. Acheulian-type large cutting tools(LCTs) such as hand-axes, picks and cleavers were indentified in the Lantian region as well. This is the first time Acheulian-type LCTs from the late Pleistocene have been identified in this region. This study distinguishes age gaps between Western world and East Asian Acheulian-type tools.展开更多
文摘Every day we experience relationships with artefacts, which describe material objects made by humans in order to reach a goal and exploit the human feature to plan ahead. Artefacts bring together cognitive evolution and technical enhancement. Although artefacts are conceived as technical, we are now facing a relationship with Information Technology （IT） artefacts. IT artefacts include both hardware and software, as a two-sided entity. The definition of IT artefact corresponds with the Saussurean linguistic sign： a two-sided entity constituted by the signifier （hardware） and the signified （software）. I claim that IT artefacts share this ontological trait with the linguistic sign. I will show that IT artefacts are the result of design and planning, while language--which is an institution--is not the fabrication of one human but linked to collective human activity.
文摘In order to develop skin artefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone nlbber and knitted nylon sheet were selected to manufacture an artificial skin, due to their higher elastic strain and high flexibility. Tensile and scissors cutting tests were conducted to characterise the matrix and reinforcing materials and the skin artefact. Material properties of the individual and the composite materials were compared with the measured properties of real octopus skin presented ill Part I. The Young＇s modulus of the skin should be below 20 MPa and the elastic strain range should be over 60%. The fracture toughness should be at least 0.9 kJ.m 2. Tubes made of the skin artefact filled with liquid were tested to study volume change under deformation. Finite element analysis model was developed to simulate the material and arm structure under tensile loading. Results show that the skin artefact developed has similar mechanical properties as the real octopus skin and satisfies all the design specifications of the OCTOPUS robot.
文摘Cone beam computed tomography (CBCT) is the modern third dimension applied in the field of oral maxillofacial region. With lower radiation dose compared to conventional CT, its applications in dentistry has increased tremendously. Artefacts can seriously degrade the quality of computed tomographic (CBCT) images, sometimes to the point of making them diagnostically unusable. To optimize image quality, it is necessary to understand why artifacts occur and how they can be prevented or suppressed. CT artifacts originate from a range of sources;physical based, scanner based and patient based. This article highlights the causes of artefacts on CBCT images and methods to avoid them.
基金supported by the National Natural Science Foundation of China (Grant Nos. U1532113, 11475170, and 11905041)the Fundamental Research Funds for the Central Universities (Grant No. PA2020GDKC0024)Anhui Provincial Natural Science Foundation, China (Grant No. 2208085MA18)。
文摘X-ray analyzer-based imaging(ABI) is a powerful phase-sensitive technique that can provide a wide dynamic range of density and extract useful physical properties of the sample. It derives contrast from x-ray absorption, refraction, and scattering properties of the investigated sample. However, x-ray ABI setups can be susceptible to external vibrations, and mechanical imprecisions of system components, e.g., the precision of motor, which are unavoidable in practical experiments. Those factors will provoke deviations of analyzer angular positions and hence errors in the acquired image data.Consequently, those errors will introduce artefacts in the retrieved refraction and scattering images. These artefacts are disadvantageous for further image interpretation and tomographic reconstruction. For this purpose, this work aims to analyze image artefacts resulting from deviations of analyzer angular positions. Analytical expressions of the refraction and scattering image artefacts are derived theoretically and validated by synchrotron radiation experiments. The results show that for the refraction image, the artefact is independent of the sample’s absorption and scattering signals. By contrast, artefact of the scattering image is dependent on both the sample’s refraction and scattering signals, but not on absorption signal.Furthermore, the effect of deviations of analyzer angular positions on the accuracy of the retrieved images is investigated,which can be of use for optimization of data acquisition. This work offers the possibility to develop advanced multi-contrast image retrieval algorithms that suppress artefacts in the retrieved refraction and scattering images in x-ray analyzer-based imaging.
文摘Objective: To propose a new method of classifying film-screen radiographic artefacts. Methodology: A prospective study was carried out at the Radiology Department of a University Teaching Hospital in Nigeria between June, 2011 and June 2013. Radiographs were assessed with the aid of a viewing box for artefacts which were arranged according to prior classifications by other researchers. They were subsequently grouped according to pre-arranged format into the new classification. Result: The following groups were observed: packaging (dark), procedure (greyscale), patient (greyscale), pre-processor (dark), processor (greyscale) and post-processor (greyscale). Conclusion: Classification of artefacts based on appearance and stage of introduction into film is easier to understand and remember.
基金supported by the One Hundred Talent Person Project of the Chinese Academy of Sciences(KZCX2-YW-BR-24)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA05130201 and XDA05120704)the National Natural Science Foundation of China(41072122 and 41202127)
文摘Eight new Palaeolithic open-air sites were identified and 770 stone artefacts were collected from 2009 to 2011 in the Lantian area of the Bahe River valley, central China. Because the famous Homo erectus fossils were unearthed at the Gongwangling and Chenjiawo localities, and more than 30 Palaeolithic open-air sites were investigated in the 1960s in this region, the catchment of Bahe River is regarded as one of the most important hominin sites from the late early Pleistocene to the middle Pleistocene. These eight newly discovered open-air sites are located at the second(n = 6), third(n = 1) or higher terraces(n = 1) of the Bahe River. The Diaozhai section on the second terrace was sampled in detail. Two samples were collected for optically stimulated luminescence dating(OSL). The OSL results suggest that a buried lithic artefact layer at the Diaozhai site spans approximately 70–30 ka. The lithic assemblage analysis suggests that the stone artefacts were made of local pebbles/cobbles such as greywacke, quartz, sandstone and igneous rocks. The main percussion techniques that were used were direct hard hammer percussion and bi-polar techniques. The lithic artefacts comprise hammer stones, cores, flakes, retouched tools and flaking debris. Acheulian-type large cutting tools(LCTs) such as hand-axes, picks and cleavers were indentified in the Lantian region as well. This is the first time Acheulian-type LCTs from the late Pleistocene have been identified in this region. This study distinguishes age gaps between Western world and East Asian Acheulian-type tools.
