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关键词： Sheet erosion   Interrill erosion   Raindrop impact   Shallow flows  

摘要： Soil erosion involves two liked processes, detachment of particles held within the soil surface by cohesive forces and inter-particle friction, and the transport of the detached material away from the site of detachment. It is commonly thought that erosion is either detachment limited or transport limited but this is not true for surfaces where raindrop driven sediment transport occurs. When detachment occurs by raindrop impact, transport away from the site of detachment can occur in the air and in rain-impacted flow. Splash transports both fine and coarse particles aerially. In rain impacted flows, fine material travels in completed suspension and at velocities that are at, or near the velocity of the flow. Coarse material may travel by raindrop induced saltation and rolling, or if flow conditions are appropriate, by flow driven saltation and rolling. Transport by splash and by raindrop induced saltation and rolling ceases when raindrop impact ceases even if previously detached material has not been discharged. Consequently, sediment transport limits erosion whenever raindrop impact is involved in transporting detached soil material over the soil surface. However, the amount of material available for transport is controlled by the ability of the impacting raindrops to cause detachment and the ability of the cohesive soil surface to resist detachment. Consequently, the discharged of coarse material by rain-impacted flows is both detachment limited and transport limited at the same time. Raindrop driven erosion is a complex process and the spatial and temporal variations in the transport mechanisms need to be considered when experiments involving raindrop driven erosion experiments are designed and the results analysed.

关键词： FLASH   linac   monitor chambers  

摘要： Purpose Recent studies of ultra-high dose rate FLASH radiotherapy show a substantial reduction of damage to normal tissue cells when compared with conventional radiotherapy. Most, if not all, of these FLASH studies have taken place using either custom research equipment or heavily modified linacs with external dosimetric control. To simplify our preclinical research efforts, we wish to deliver FLASH with a minimally modified linac using the internal dosimetric system. Methods To enable the built-in monitor chambers to terminate a FLASH beam, we reversibly modified an Elekta linear accelerator previously fit with a high dose rate electron (HDRE) system to include additional resistance in the signal path from the monitor chambers to the dose control system. To produce the FLASH beam, we altered the energy calibration tables of a decommissioned HDRE beam to functionally produce a photon mode beam current exiting through the electron window of the linac. We then used the machine modifications to assist in beam tuning and to calibrate the monitor chambers for FLASH delivery. We employed a radiochromic film for external dosimetry and preliminary tests of monitor chamber dosimetric stability. Results We identified attenuation values and distributions that reduced the overall signal from the monitor chambers to the dose control system such that the system could terminate the beam without input from external monitoring circuits. Calibration of the control system resulted in 12 MU per second, constituting roughly 180 Gy at the mylar window. Preliminary tests indicate a linear MU to dose relationship at FLASH dose rates, but we encountered challenges in both dose resolution and repeatability of beam termination. Conclusions The addition of attenuation in the control system path from the monitor chambers is fundamentally identical to current HDRE system design and was achieved without significant modification of the accelerator. Preliminary results indicate that current-generat

关键词： Computer-assisted orthopedic surgery (CAOS)   Extreme lateral interbody fusion (XLIF)   Head-mounted display   Lateral lumbar interbody fusion   Lumbar degenerative spondylolisthesis   Lateral decubitus position   Navigation-assisted XLIF (NALIF)   Wearable smart glasses  

摘要： BACKGROUND: We describe a new technique that combines navigation-assisted extreme lateral interbody fusion (NALIF) and percutaneous placement of pedicle screws in the lateral decubitus position with the surgeon using wearable smart glasses. METHODS: We explain our method for nonfluoroscopic NALIF and single-position (SP)-percutaneous pedicle screw (PPS) surgery for patients with degenerative lumbar diseases using wearable smart glasses. The wearable smart glasses provide a semitransparent overlay of the navigation information onto the image seen through the lenses. This technique does not require fluoroscopy during lateral interbody fusion or PPS insertion. It is convenient because it does not require a Jamshidi needle or guidewire when inserting PPSs. RESULTS: Using this method, the surgeon can glance at the 3-dimensional images on the wearable smart glasses while still viewing the operation field. A review of 24 cases yielded an average operation time of 89.5 +/- 16.4 minutes and 66.7 +/- 67.0 mL of blood loss, without any severe intra-or postoperative complications. CONCLUSIONS: Nonfluoroscopic NALIF and SP-PPS placement surgery is a safe and effective means for implanting cages and PPSs in this minimally invasive approach without compromising the results. Although further investigations are needed, the wearable smart glasses may be a useful surgical aid when performing NALIF and SP-PPS placement in patients with degenerative lumbar diseases.

关键词： supraclavicular artery island flap   pharyngeal reconstruction   head and neck cancer   reconstruction   oncology   technical note  

关键词： Performance feedback   Teacher emotions   Teacher burn-out  

摘要： This paper is in response to the manuscript entitled, "Success, failure and emotions: Examining the relationship between performance feedback and emotions in diagnostic reasoning," (Jarrell, Harley, Lajoie, & Naismith, Educational Technology & Research Development, 65, 1263-1284: 2017) from a K-12 teacher and administrator educational perspective. Jarrell et al.'s (Educational Technology & Research Development, 65, 1263-1284: 2017) findings indicate a strong relationship between outcome emotions and performance tasks: highest performing medical students had the most positive emotions. The authors suggested that medical students who fail and experience negative emotions could experience a loss of confidence and lead to dropping out of medical school. These results can be applied to teachers and administrators in K-12 settings as they make the shift to digital learning by including emotional assessments into the new digital learning platforms in order to address areas of emotional stress and teacher burnout before leading to attrition. This perspective makes suggestions of ways Jarrell et al.'s (Educational Technology & Research Development, 65, 1263-1284: 2017) findings could be a starting place for educational stakeholders to prioritize teachers' emotional well-being and offer an opportunity to provide intervention support in order to increase teacher self-efficacy in the shift to digital and possibly reduce teacher burnout.

关键词： automatic exposure control   CT   CTDI phantom   image quality   spatial concordance   tube current modulation  

摘要： Purpose To assess the utility of the standard body CTDI phantom in characterizing the operation scheme of tube current modulation (TCM) systems in CT. Methods The body CDTI phantom was used to characterize two TCM systems: TCM1 and TCM2, implemented in scanners from different vendors. The phantom was aligned at the gantry isocenter in two configurations. In configuration A, the facet planes of the phantom were parallel to the patient table, while in configuration B they were vertical to the patient table and parallel to the patient's long axis. Acquisitions were performed using the routine abdominal examination protocol. mA(z) profiles were recorded from images' DICOM header. The water equivalent diameter (d(w)) and oval ratio (OR) were calculated as a function of z-axis location. Image noise was defined as the standard deviation (SD) of the mean Hounsfield unit value measured in a region of interest at the center of the phantom's image. Regression analysis was performed to modulated mA and SD vs d(w) and OR. The spatial concordance between the change in phantom size and change in mA (SCmA) was calculated as the percent difference in the slope of mA(z) change between the 1st and 2nd half of the phantom. The corresponding spatial concordance between the change in phantom size and change in image noise (SCnoise) was calculated. Results Modulated mA(z) along the z-axis did not substantially differentiate between configurations A and B. Correlation between ln(mA) and OR was found to be higher compared to correlation between ln(mA) and d(w). SCmA was 48% for TCM1 and 33% for TCM2. The corresponding SCnoise was 29% for TCM1 and 16% for TCM2. Conclusion Apart from routine CT dosimetry evaluations, the standard CTDI phantom positioned in configuration A or B may additionally be used by medical physicists to evaluate the performance of TCM operational characteristics.

关键词： 英语课堂   跨文化   策略探讨  

摘要： 随着世界经济的不断融合,各国之间的文化产生了诸多碰撞,对各国交际产生了巨大的影响。在小学英语教学中培养学生的跨文化交际意识,为学生的英语学习发展奠定良好基础十分重要。

关键词： Computational fluid dynamics   Ventilation   Firing range   Firing emissions   Frangible ammunition   Reynolds-averaged Navier-Stokes  

摘要： Firing ranges critically depend on ventilation systems to minimize the exposure of personnel to ammunition refuse. A numerical analysis utilizing a computational fluid dynamics (CFD) method was used to simulate the ventilation system and predict airflow patterns within a 122-foot long, military firing range housing 21 firing stalls. The intent for this model was to identify back circulation causing firing emissions to entrain in occupied areas. Measured values at several locations within the facility were used for either input values in the model or for validation of the model solution. The analysis evaluated massless particles released at three heights to correspond with standing, kneeling, and prone firing positions. Additional predictions were completed using the recommended technical guidance for ventilation of small arms firing ranges to compare against flow dynamics of the current system. The results revealed particles circulating back behind the shooter and into the personnel occupied area. Lower supply air velocities correspond to more uniform flow and successful movement of particles downrange in the small arms firing range under investigation. The ventilation air velocity at the firing line recommended by the design guide was not achieved consistently despite the supply air velocity being set to design guide values. Overall, the results demonstrated that CFD models are useful aides for optimizing supply air velocities in current firing range facilities and for evaluating and developing design standards that provide the proper ventilation required for the health and safety of building occupants.

关键词： General Public   Safety/Hazards   Distance Learning/Self Instruction   Internet/Web-Based Learning   Student-Centered Learning  

摘要： Educational resources that cover essential knowledge related to chemistry safety rules are openly accessible on the CHIMACTIV website (http://***/). Organized into two online tracks, the content covers personal and collective protections, first aid, as well as the handling of hazardous chemicals. Being interactive and abundantly illustrated by photos and videos, these resources may be used by teachers to encourage (or even oblige) their students to self-train before lab sessions. Our user experience shows that students improve their chemical safety knowledge and culture upon consulting these resources: they arrive in the lab more confident and are more attentive to safety rules (especially concerning safety glasses and gloves), with a deeper knowledge of chemical hazards and of waste management options. Thanks to their digital responsiveness, these open resources may also be accessible during the lab sessions, enabling the students to get the information "just-in-time". In addition, decision trees for liquid and solid waste management are available, helping the students to gain reflexivity as well as to acquire good laboratory practice during lab sessions. In this way, the supervisors of the practical work sessions waste much less time taking back students who do not follow the safety rules properly.