Open Position Research Articles

Dynamic behaviour of ultra-high performance concrete beams with rectangular openings subjected to impact loads

To facilitate residents’ needs, contemporary building structures often incorporate prefabricated transverse openings in reinforced concrete (RC) beams to accommodate pipeline installations. However, these openings can potentially impact the load-bearing capacity of the beams, particularly as structures increasingly need to consider dynamic loading effects. The use of ultra-high performance concrete (UHPC) has proven effective in enhancing the dynamic resistance of RC beams with openings. This study employs numerical simulations in ANSYS/LS-DYNA to investigate the dynamic response of UHPC beams with rectangular openings exposed to low-velocity impact. The calibrated Continuous Surface Cap (CSC) model is primarily validated through quasi-static four-point loading tests on UHPC beams with openings. Following this validation, numerical simulations of drop hammer impact are carried out to comprehensively analyse the behaviour of UHPC beams with openings. Furthermore, parametric investigations are performed to evaluate the impact response of UHPC beams with large or small openings, considering various design factors such as opening size, opening position, stirrup quantity and UHPC strength level.

The mechanical environment regulates the extent of aortic valve calcification and thickness: an ex vivo whole mouse heart study

Abstract Background Aortic stenosis (AS) is a narrowing of the aortic valve opening due to calcification and thickening of the leaflets. Calcifications are mostly located at regions with high mechanical stress and disturbed flow suggesting that mechanical environment is important in the regulation of calcification. However, direct evidence linking valve calcification and mechanical stress is still lacking. Recently, we established an ex vivo calcification model for whole mouse hearts (Miniature Tissue Culture System MTCS) which allows the study of the mechanical environment underlying aortic valve calcification. Purpose Aim of this study was to investigate the role of mechanical stress on aortic valve calcification and thickening using the MTCS. Methods Whole mouse hearts were cultured in the MTCS with 2 distinct configurations: 1) medium flowing from the aorta towards the aortic valve to create a continuous closed aortic valve (n=28) and 2) medium flowing from the left ventricle through the aortic valve towards the aorta to create a continuous open aortic valve (n=17) (Figure1). The hearts were subjected to low (300 ul/min) or high (3000 ul/min) flow speed in the presence of calcifying medium (3mM phosphate buffer). After culture for 1 week, the hearts were isolated and fixed overnight with 4% PFA/PBS. Alizarin red staining was performed to determine calcification presence. Quantifications were performed using Caseviewer software. Results Aortic valves in closed configuration exposed to a high flow speed, exhibited significant increase in calcification compared to aortic valves in the closed configuration exposed to low flow speed or aortic valve cultured in the open position (p<0.01, Figure2A). Of interest, the extent of calcification in the aortic valve in closed position exposed to high flow speed strongly correlated with the diameter of the aortic annulus (R²=0.86, p<0.0001, Figure2B). Conversely, leaflet thickness was significantly lower in the closed aortic valve configuration as compared with the open aortic valves configuration (p<0.05, p<0.001, Figure2C). Conclusion Our study demonstrates the influence of mechanical environment on aortic valve calcification and thickening. The presence of calcification in the closed but not the open aortic valve configuration exposed to high flow suggests that increased pressure promotes calcification. The correlation of the extent of aortic valve calcification with the diameter of the aortic annulus implies that configuration of the valve is an important determinator of calcification, with potential implications for the results of aortic valve repair. The presence of a minimal amount of mechanical stress as experienced by aortic valves in the open position, however, resulted in thicker aortic valves, indicating that the right balance of mechanical stresses is required to maintain normal valve morphology. These findings provide valuable insights into AS pathogenesis, guiding future therapeutic approaches.ex vivo cultured aortic valvesCalcification in ex vivo aortic valves

Preservice Librarians and Principals' Hiring Practice

Every year, principals face the challenge of hiring staff to fill the open positions on their campus and may only hire one or two school librarians during their tenure. School principals can build a cohesive team to help ensure student success by hiring staff with strong leadership skills. School librarian preparation standards suggest that school librarians be educated to serve as leaders (American Library Association, American Association of School Libraries, & Council for the Accreditation of Educators Preparation, 2019). Moreover, the American Association of School Librarians (AASL) advocates for the leadership role of school librarians in its mission statement (2018). Research indicates that transformational leadership behaviors apply to school librarians because they interact with the entire school community and may serve as change agents to positively transform their school’s culture (Smith, 2011). This study posits that principals often hire preservice school librarians instead of experienced school librarians. Therefore, there is a need to understand the relationship between the hiring criteria identified by principals and the leadership role specified in the school librarian standards. This mixed-methods study examines the criterion principals use to hire librarians and their alignment with the transformational leadership behaviors of preservice librarians.

Influence of opening shape, size and position on the ultimate strength, stiffness and energy dissipation of confined brick masonry walls

Influence of opening shape, size and position on the ultimate strength, stiffness and energy dissipation of confined brick masonry walls

Observation of dynamic position and morphological changes of temporomandibular joint discs under Angle's classification

Objective: To observe the dynamic changes of the temporomandibular joint (TMJ) disc in joint movement under different Angle's classification, providing reference for understanding joint functional movement and providing a basis for more accurate clinical imaging diagnosis. Methods: A total of 30 patients (13 males and 17 females) with temporomandibular disorders who were admitted to Beijing Friendship Hospital, Capital Medical University and General Hospital of the People's Liberation Army from January 2022 to April 2024 were enrolled. Thirty adults (13 males and 17 females) with different Angle's classification, with an average age of (34.4±8.5) years, were subjected to dynamic imaging of their TMJ from the closed position to the maximum opening position, and then to the closed position using MRI. The position and morphological changes of the articular discs were observed. Results: The results showed that volunteers with no displacement of the articular disc in class Ⅰ, Ⅱ, and Ⅲ relationships had different shapes of the articular disc during open and closed mouth movements. However, in the maximum opening position, the articular disc were all located directly below the maxillary nodules, and their shape is double concave. In terms of irreversible anterior displacement of the articular disc, in class Ⅰ Angle, the posterior zone of the disc contacts the anterior inclined plane of condyle from the maximum opening position back to the front of the closing position. In class Ⅱ, the posterior zone of the disc contacts the anterior inclined plane of condyle from the beginning of opening position to maximum opening position. In class Ⅲ, the posterior zone of the disc is always in contact with the anterior inclined plane of condyle throughout the entire movement process. And among them, the articular disc presents a forward displacement state at the closing position, its morphology undergoes folding phenomenon. When the openness is 2.5 cm, the articular disc moves up to a certain extent, and is closer to the anterior inclined plane of condyle, and its shape is also partially changed. When the openness is 4.3 cm, the shape of the articular disc, located between the anterior inclined plane of the joint node and the posterior inclined plane of the condyle, is typical double concave, which is sufficient to show that the articular disc is reversible when maximum opening position is reached. In terms of reversible anterior disc displacement, in class Ⅰ Angle, the posterior zone of the disc contact with the anterior inclined plane of condyle at the beginning of the opening position and the end of the closing position. In classⅡ Angle, the posterior zone of the articular disc is not in contact with the anterior inclined plane of condyle. In class Ⅲ Angle, the posterior zone of the articular disc contact with the anterior inclined plane of condyle at the end of the closing position. Conclusions: Multi level dynamic MR imaging data of the temporomandibular joint can dynamically observe the movement of the temporomandibular joint, intuitively and accurately display the position and shape of the articular disc during movement, and can serve as a useful supplement to static conventional MR imaging of the TMJ. The patient's TMJ needs to reach the maximum opening position in order to determine whether the joint disc displacement can be reversible or not.

Study on the structural behavior and reinforcement design of openings in subway station floor slabs

This paper investigates the structural behavior of openings in subway station floor slabs through model experiments and finite element simulation. The study analyzes the effects of the opening's aspect ratio, dimensions, and position on the stress characteristics of various structural components. Based on the stress levels and failure characteristics at different locations in the station structure, three reinforcement schemes are proposed: adding corner fillets, installing buttress columns, and adding ring beams. Comparative analysis with the original structure's internal forces and displacement patterns reveals the effectiveness of each reinforcement scheme. The results show that openings reduce the moment of inertia of the floor slab cross-section, weakening the slab's stiffness and making the area around the openings and slab-column joints prone to local damage. Increasing the aspect ratio of the opening, enlarging its dimensions, or closely arranging multiple openings diagonally reduces the local load-bearing capacity of the structure. Adding corner fillets can reduce the maximum equivalent stress in the slab by more than 15 %, alleviating stress concentration caused by the openings. Buttress columns and ring beams increase the stiffness of the side walls, distribute the lateral forces causing wall bending moments, and enhance the structure's resistance to lateral displacement.

Negative Externalities of Regulation: Identity‐relevant Information in Mandatory Short‐selling Disclosures

Since November 2012, short sellers have been required to disclose all their significant short positions against European firms. While this regulation was primarily implemented to have implications for financial markets, I explore its negative externalities on shorted firms. Using mandatory disclosures of short positions between 2013 and 2019, I find that short‐selling notifications and the number of short sellers with an open short position are positively associated with shorted firms’ dividend policies. Notably, the association is more pronounced for upward and initial notifications compared to downward and follow‐up notifications. These results are robust to several matching methods and a battery of robustness tests. Additional results reveal that shorted firms might increase their dividends because short‐selling disclosures reveal the identity of active and large short sellers, highlighting the importance of short sellers’ heterogeneity. I also show that shorted firms increase their dividends temporarily and do not react homogenously, as they engage in a cost–benefit analysis to decide whether to use their dividend policy. Overall, I document the real effects on shorted firms of an alternative form of short selling, bridging the gap between passive and activist short selling. I conclude that mandatory short‐selling disclosure regimes carry negative externalities for firms due to the provision of short sellers’ identity‐relevant information.

Sound insulation of partially open windows - alternative laboratory measurement methods

Sound insulation with partially open windows has had growing attention in recent years. In Denmark, this is primarily caused by the Danish Environmental Protection Agency's guideline from 2007 "Noise from roads", which introduces noise limits with open windows (opening area of 0.35 m2) for situations with a high traffic noise level. The sound insulation of traditional windows in open position have been measured in both the laboratory and external environment, and for certain setups too different results have been observed. To investigate the reasons behind the discrepancies, the traditionally reverberant source room of laboratory measurements was modified to a semi-anechoic room to remove reflections from unwanted reflections from room surfaces and to imitate the external environment during field measurements. Four different window types were tested as part of the research projects "Optimized measurement method for sound reduction of partially open windows part 1 and 2" (MetÅV and MetÅV2) in collaboration with four Danish window manufacturers. The primary focus of the project is to explore alternative laboratory methods to the traditional diffuse field method by studying reference cases from field measurements and taking into consideration different sound source positions and window geometry. This paper describes the results so far.

Free vibration analysis of bio-inspired helicoidal laminated composite square and annular plates having circular openings using isogeometric analysis

Present work aims to carry out free vibration analysis of bio-inspired helicoidal laminated composite square and annular-shaped plates with circular openings. Refined plate theory, created within the context of isogeometric analysis (IGA) is used during the present study. The theory is coded in MATLAB to study the behavior of the plates and the results are validated with the frequencies obtained using ABAQUS. Recursive, semi-circular, exponential, and Fibonacci helicoidal schemes are used during the present study for studying the free vibration behavior and the frequency is compared with the conventional cross-ply and quasi-isotropic laminates. Influence of position of opening, dimensions of opening, number of plies, and end condition, on the free vibration behavior of square and annular shaped bio-inspired helicoidal plates is carried out. The plates with CCCC and CCCF ends having openings at the quarter length are found to have higher frequency by 3.518 % and 0.3897 % compared to the values of the frequency of the plate with opening at the centre with the same perimeter. Opposite trend is observed for plate with PPPP, CFCF, and CFFF end conditions, where the plate with opening at centre exhibits higher value of the frequency by 2.427 %, 0.821 %, and 1.232 %, respectively. When the opening is near to the corners, the decrease in frequency by 3.913 %, 1.576 %, 1.193 %, and 1.437 % is observed for CCCC, CCFF, CCCF, and CFCF end conditions while increase by 1.490 % and 2.717 % is observed for the CFFF and PPPP end conditions. The mode shape of the plate is found to be greatly influenced by the position and dimension of the hole and end conditions of the plate.

Evaluation of the Position and Area of Window Openings on Visual Comfort in Classrooms at Budi Luhur University

Abstract Window openings in classrooms at Budi Luhur University use glass coated with ray ben stickers to reduce excess heat entering the classroom with different levels of darkness. This can cause the distribution of light in the classroom to be uneven and the light intensity requirements not to meet standards. This research is essential to determine the most efficient and effective position and area of classroom window openings, as well as to propose a window opening design that meets visual comfort standards. The research method used in this research is a quantitative research method with an experimental approach. The Quantitative Method is measuring the intensity of natural lighting in window openings and calculating the area of window openings in classrooms in units 3, 4, 5, 6 of Budi Luhur University, as well as processing questionnaire data about space perception. The results of this research are that the best position and type of window openings are grouped windows with ¾ openings, the lighting intensity is closest to SNI Lighting, namely class 4.3.1, which is 134 lux when the lights are off and 168 lux when the lights are on. The best perception of visual comfort felt by respondents was in classroom 4.3.1, namely 94% of respondents stated that they were visually comfortable when the lights were off, and 93% of respondents stated that they were visually comfortable when the lights were turned on.

Creating And Accelerating The Shift From Fossil Fuel Jobs To Green Energy Jobs

The green energy job market in the United States is growing consistently, whereas fossil fuel employment is declining. Green energy jobs have overtaken fossil fuel jobs in electric power generation (EPG), and they are beginning to command a presence in the fuels sector. Demand for green energy workers is very high, and green energy employers are having trouble finding qualified workers to fill their open positions. Real wages in green energy are increasing, the jobs are stable, and workers have more choice as to which parts of the US they want to live in. Meanwhile, workers are being pushed out of fossil fuel jobs, and this has caused fossil fuel dependent communities to languish. However, workers pushed out of fossil fuel industries are not shifting to green energy jobs, despite their attractive qualities. This is caused by numerous, major barriers. However, solutions are starting to form amongst major institutions such as the Brookings Institute and the New York Times, showcasing that there is a real problem and potential for opportunity in this area. A possible solution is to take this job transition online, consolidating the workers, employers, and necessary re-training in one place

Correlations of temporomandibular joint morphology and position using cone-beam computed tomography and dynamic functional analysis in orthodontic patients: A cross-sectional study.

To correlate temporomandibular joint (TMJ) morphology and position with cone-beam computed tomography (CBCT) images, Joint Vibration Analysis (JVA), and Jaw Tracker (JT) to develop a radiation-free, dynamic method for screening and monitoring the TMJ in orthodontic patients. A total of 236 orthodontic patients without symptoms of TMJ disorders who had undergone CBCT were selected for the JVA and JT tests in this cross-sectional study. TMJ position and morphology were measured using a three-dimensional analysis software. JT measurements involved six opening-closing cycles, and JVA measurements were performed using a metronome to guide the mouth opening-closing movements of the patients. The correlations among the three measuring devices were evaluated. Abnormalities in condylar surface morphology affected the mandibular range of motion. The cut-off value results show that when various measurement groups are within a certain range, abnormalities may be observed in morphology (area under the curve, 0.81; P < 0.001). A 300/< 300 Hz ratio ≥ 0.09 suggested abnormal morphology (P < 0.05). Correlations were observed among the maximum opening velocity, maximum vertical opening position, and joint spaces in the JT measurements. Correlations were also observed between the > 300/< 300 Hz ratio, median frequency, total integral, integral < 300 Hz, and peak frequency with joint spaces in the JVA measurements. JT and JVA may serve as rapid, non-invasive, and radiation-free dynamic diagnostic tools for monitoring and screening TMJ abnormalities before and during orthodontic treatment.

Trends in dental school faculty: An analysis of the results of the 2021‒2022 ADEA Dental School Faculty Demographic Census and 2018‒2019 ADEA Survey of Dental School Faculty.

Each year, American Dental Education Association (ADEA) collects data on U.S. dental school faculty demographics, compensation, and vacant and lost positions. One of the purposes of the reports associated with this project is to provide information to U.S. dental schools on national trends on dental school faculty. This report examines the landscape of faculty workforce at U.S.-accredited dental schools in 2021‒2022 and changes relative to the 2018‒2019 academic year. The information contained within this report includes faculty position information, new and separated faculty, open or vacant faculty positions, lost faculty positions, and faculty demographics. The report analyzes data from the 2018‒2019 ADEA Survey of Dental School Faculty (representing an estimated 91% of the full-time and part-time faculty) and 2021‒2022 ADEA Dental School Faculty Salary and Demographic Census (an estimated 84% of the faculty). The analysis revealed that more than half of dental school faculty was in the south and northeast in 2021‒2022. Among responding schools, 85% of the faculty concentrated on teaching, research, and training in 2021‒2022, a proportion similar with 2018‒2019. One in five faculty was tenured or on tenure track, similar with 2018‒2019. More than three-quarters of full-time and part-time faculty were clinical faculty in 2021‒2022. There was a 62% increase in open faculty positions between 2018‒2019 and 2021‒2022. Women accounted for four in 10 faculty members in 2021‒2022-more than 3 years before. The median age of dental school faculty declined from 56 to 54 years old between 2019 and 2022. This study found that dental school faculty was increasingly younger, with more women members and more open positions in 2021‒2022 than in 2018‒2019.

Which is better to decompress the nerve roots in cervical radiculopathy: stretching or traction from foraminal opening position?

Which is better to decompress the nerve roots in cervical radiculopathy: stretching or traction from foraminal opening position?

Simplified Direct Strength Method for the design of cold-formed steel channels with circular web openings under two-flange loadings

Previous studies have put forward reduction factor equations to determine the web crippling strength of cold-formed steel (CFS) channels with circular web openings. However, these equations overlook vital parameters such as material yield strength, flange width, and fillet radius of CFS channels. Consequently, this paper introduces simplified Direct Strength Method (DSM) equations, which account for plastic loads (Py) and elastic buckling loads (Pcr), integrating the aforementioned crucial parameters. Eight unique yield line models were devised, considering two-flange loadings: interior-two-flange (ITF) and end-two-flange (ETF), as well as the positioning of circular web openings, to compute the yield line length for Py. Similarly, new Pcr equations were also proposed. The reliability of the proposed equations was evaluated using a dataset of 236 test results sourced from the literature. This assessment aims to demonstrate the suitability of the equations for incorporation into future revisions of international design codes.

Numerical Investigation of Cross Ventilation Flow in A Gable Roof Building with Asymmetric Opening Positions

Natural ventilation can be a suitable alternative to mechanical ventilation as it is cost-effective and environmentally friendly. Therefore, an effective design of the natural ventilation system is very crucial. In this work, an attempt has been made to investigate the impact of opening positions and roof pitch on the performance of wind-induced cross-ventilation in a gable roof building. Numerical simulations were carried out using the computational fluid dynamics (CFD) technique based on the steady Reynolds averaged Navier-Stokes equations (RANS) model. Six configurations with asymmetric openings on opposite facades were considered to evaluate the effect of opening positions. Further, for studying the influence of roof pitch on the flow properties, three roof pitches, viz. 3:10, 5:10 and 7.5:10 were considered. It is found that the configuration with a windward opening in the middle and a leeward opening at the bottom (Configuration D) has the highest flow rate. The configuration with a windward opening at the top and a leeward opening at the bottom (Configuration B) has the lowest flow rate. Furthermore, the investigation with different roof pitches reveals that buildings with lower roof pitches are more vulnerable to wind loading due to higher flow separation at the windward eave. The investigation concludes that the opening position and roof pitch significantly influences the indoor airflow characteristics thereby affecting the ventilation performance.

Study on calculation model of deflection of prefabricated hole bulkhead under the action of internal explosion

In order to study the plastic deformation law of ship plate frames under the coupling action of internal explosion load and fragment, first, the calculation formula of plastic deformation deflection of the non-porous plate is derived through the law of conservation of energy. According to the numerical calculation results, the influence of the opening position and opening area of the target plate on the deflection gain of the target plate is further explored. The mathematical expression form of the opening area and opening position on the deflection gain of the prefabricated target plate is fitted, and then, the deflection calculation model of the prefabricated target plate is established. It can theoretically predict the deflection of the bulkhead under cabin explosion and has a certain application reference value for ship cabin anti-explosion design and internal explosion damage assessment.

Optic Nerve Head Morphology and Macula Ganglion Cell Inner Plexiform Layer Thickness in Axially Anisometropic Rhesus Monkeys.

The purpose of this study was to determine the effects of axial elongation on optic nerve head morphology and macula inner retinal thickness in young rhesus monkeys. Both eyes of 26 anisometropic, 1-year-old rhesus monkeys were imaged using optical coherence tomography (OCT). Before imaging, the animals were sedated, their eyes were dilated, and axial length was measured using an optical biometer. OCT imaging included a 20 degrees, 24-line radial scan centered on the optic nerve head (ONH) and two 20 degrees × 20 degrees raster scans, one centered on the ONH and the other on the macula. Radial scans were analyzed using programs written in MATLAB to quantify the Bruch's membrane opening (BMO) area and position, minimum rim width (MRW), anterior lamina cribrosa surface (ALCS) position, size of any scleral crescent, circumpapillary retinal nerve fiber layer (RNFL), and choroid thickness (pCh). Macula total retinal thickness (mTRT) and ganglion cell inner plexiform layer (GCIPL) thicknesses were quantified from macula scans. Linear least square regression was determined for OCT measures and axial length of the right eye, and for inter-eye differences. Animals were 341 ± 18days old at the time of imaging. BMO area (R2 = 0.38), ALCS position (R2 = 0.45), scleral crescent area (R2 = 0.35), pCh thickness (R2 = 0.21), mTRT (R2 = 0.24), and GCIPL thickness (R2 = 0.16) were correlated with the axial length (all P < 0.05). For each of these parameters, the right-eye regression slope did not differ from the slope of the interocular difference (P > 0.57). There are posterior segment morphological differences in anisometropic rhesus monkeys related to axial length. Whether these differences increase the risk of pathology remains to be investigated.

Research on Residential Interior Design and Energy Saving Optimization with Sustainable Low-carbon Development

The escalating crisis of global warming, driven by the emission of greenhouse gases, poses a formidable challenge for humanity as a whole. Notably, the construction industry contributes significantly to the global greenhouse gas inventory. Consequently, prioritizing low-carbon construction assumes paramount importance in mitigating the pervasive impact of the greenhouse effect on a global scale. Such an endeavor stands as a crucial safeguard for ensuring the sustainable development of human civilization. Therefore, from the perspective of low- carbon building design optimization research is an important part of low-carbon building. From the perspective of architectural design, this paper summarizes that low-carbon building design should pay attention to following aspects: reasonable use of natural lighting and natural ventilation, reduce the carbon emission value of building use stage; Taking the transformation project of the former engineering Institute of Southeast University as an example, this paper probes into the effect of design optimization on reducing carbon emissions, and quantitatively studies the relationship between the design optimization of lighting, ventilation and envelope structure materials and the reduction of building carbon emissions. The Angle selection of roof skylight is studied from the Angle of day- lighting optimization, the size and position of facade opening and the strategy of natural ventilation path are studied from the Angle of ventilation optimization. The indoor ventilation further reduces the refrigeration energy consumption, which is 22.1% less than before the renovation, and the roof reduces the heat gain by 22%-32%.e.

A Working Conditions Warning Method for Sucker Rod Wells Based on Temporal Sequence Prediction

The warning of the potential faults occurring in the future in a sucker rod well can help technicians adjust production strategies in time. It is of great significance for safety during well production. In this paper, the key characteristic parameters of dynamometer cards were predicted by a temporal neural network to implement the warning of different working conditions which might result in failures. First, a one-dimensional damped-wave equation was used to eliminate the dynamic loads’ effect of surface dynamometer cards by converting them into down-hole dynamometer cards. Based on the down-hole dynamometer cards, the characteristic parameters were extracted, including the load change, the position of the valve opening and closing point, the dynamometer card area, and so on. The mapping relationship between the characteristic parameters and working conditions (classification model) was obtained by the Xgboost algorithm. Meanwhile, the noise in these parameters was reduced by wavelet transformation, and the rationality of the results was verified. Second, the Encoder–Decoder and multi-head attention structures were used to set up the time series prediction model. Then, the characteristic parameters were predicted in a sequence-to-sequence way by using historical characteristic parameters, date, and pumping parameters as input. At last, by inputting the predicted results into the classification model, a working conditions warning method was created. The results showed that noise reduction improved the prediction accuracy significantly. The prediction relative error of most characteristic parameters was less than 15% after noise reduction. In most working conditions, their F1 values were more than 85%. Most Recall values could be restored to over 90% of those calculated by real parameters, indicating few false negative cases. In general, the warning method proposed in this paper can predict faulty working conditions that may occur in the future in a timely manner.