Wake Structures and Surface Patterns of the DrivAer Notchback Car Model under Side Wind Conditions

The flow field topology of passenger cars considerably changes under side wind conditions. This changes the surface pressure, aerodynamic force, and drag and performance of a vehicle. In this study, the flow field of a generic passenger vehicle is investigated based on three different side wind angles. The study aimed to identify vortical structures causing changes in the rear pressure distribution. The notchback section of the DrivAer model is evaluated on a scale of 1:4. The wind tunnel tests are conducted in a closed section with a splitter plate at a Reynolds number of 3 million. The side wind angles are 0∘ , 5∘ , and 10∘ . The three-dimensional and time-averaged flow field downstream direction of the model is captured by a stereoscopic particle image velocimetry system performed at several measurement planes. These flow field data are complemented by surface flow visualizations performed on the entire model. The combined approaches provide a comprehensive insight into the flow field at the frontal and side wind inflows. The flow without side wind is almost symmetrical. Longitudinal vortices are evident along the downstream direction of the A-pillar, the C-pillars, the middle part of the rear window, and the base surface. In addition, there is a ring vortex downstream of the vehicle base. The side wind completely changes the flow field. The asymmetric topology is dominated by the windward C-pillar vortex, the leeward A-pillar vortex, and other base vortices. Based on the location of the vortices and the pressure distributions measured in earlier studies, it can be concluded that the vortices identified in the wake are responsible for the local minima of pressure, increasing the vehicle drag

Positioning in time and space: cost-effective exterior orientation for airborne archaeological photographs

Since manned, airborne aerial reconnaissance for archaeological purposes is often characterised by more-or-less random photographing of archaeological features on the Earth, the exact position and orientation of the camera during image acquisition becomes very important in an effective inventorying and interpretation workflow of these aerial photographs. Although the positioning is generally achieved by simultaneously logging the flight path or directly recording the camera's position with a GNSS receiver, this approach does not allow to record the necessary roll, pitch and yaw angles of the camera. The latter are essential elements for the complete exterior orientation of the camera, which allows – together with the inner orientation of the camera – to accurately define the portion of the Earth recorded in the photograph. This paper proposes a cost-effective, accurate and precise GNSS/IMU solution (image position: 2.5 m and orientation: 2°, both at 1σ) to record all essential exterior orientation parameters for the direct georeferencing of the images. After the introduction of the utilised hardware, this paper presents the developed software that allows recording and estimating these parameters. Furthermore, this direct georeferencing information can be embedded into the image's metadata. Subsequently, the first results of the estimation of the mounting calibration (i.e. the misalignment between the camera and GNSS/IMU coordinate frame) are provided. Furthermore, a comparison with a dedicated commercial photographic GNSS/IMU solution will prove the superiority of the introduced solution. Finally, an outlook on future tests and improvements finalises this article

Accuracy analysis of direct georeferenced UAV images utilising low-cost navigation sensors

Unmanned aerial vehicles (UAVs), also known as unmanned airborne systems (UAS) or remotely piloted airborne systems (RPAS), are an established platform for close range airborne photogrammetry. Compared to manned platforms, the acquisition of local remote sensing data by UAVs is a convenient and very flexible option. For the application in photogrammetry UAVs are typically equipped with an autopilot and a lightweight digital camera. The autopilot includes several navigation sensors, which might allow an automated waypoint flight and offer a systematic data acquisition of the object resp. scene of interest. Assuming a sufficient overlap between the captured images, the position (3 coordinates: x, y, z) and the orientation (3 angles: roll, pitch, yaw) of the images can be estimated within a bundle block adjustment. Subsequently, coordinates of observed points that appear in at least two images, can be determined by measuring their image coordinates or a dense surface model can be generated from all acquired images by automated image matching. For the bundle block adjustment approximate values of the position and the orientation of the images are needed. To gather this information, several methods exist. We introduce in this contribution one of them: the direct georeferencing of images by using the navigation sensors (mainly GNSS and INS) of a low-cost on-board autopilot. Beside automated flights, the autopilot offers the possibility to record the position and the orientation of the platform during the flight. These values don’t correspond directly to those of the images. To compute the position and the orientation of the images two requirements must be fulfilled. First the misalignment angles and the positional differences between the camera and the autopilot must be determined (mounting calibration). Second the synchronization between the camera and the autopilot has to be established. Due to the limited accuracy of the navigation sensors, a small number of ground control points should be used to improve the estimated values, especially to decrease the amount of systematic errors. For the bundle block adjustment the calibration of the camera and their temporal stability must be determined additionally. This contribution presents next to the theory a practical study on the accuracy analysis of direct georeferenced UAV imagery by low-cost navigation sensors. The analysis was carried out within the research project ARAP (automated (ortho)rectification of archaeological aerial photographs). The utilized UAS consists of the airplane “MAJA”, manufactured by “Bormatec” (length: 1.2 m, wingspan: 2.2 m) equipped with the autopilot “ArduPilot Mega 2.5”. For image acquisition the camera “Ricoh GR Digital IV” is utilised. The autopilot includes a GNSS receiver capable of DGPS (EGNOS), an inertial measurement system (INS), a barometer, and a magnetometer. In the study the achieved accuracies for the estimated position and orientation of the images are presented. The paper concludes with a summary of the remaining error sources and their possible corrections by applying further improvements on the utilised equipment and the direct georeferencing process

Determinants of patient satisfaction following reconstructive shoulder surgery

Background Obtaining patient satisfaction is a key goal of surgical treatment. It was the purpose of this study to identify pre-, peri- and postoperative factors determining patient satisfaction after shoulder surgery, quantify their relative importance and thereby allow the surgeon to focus on parameters, which will influence patient satisfaction. Methods We retrospectively reviewed 505 patients, who underwent either rotator cuff repair (n = 216) or total shoulder arthroplasty (n = 289). We examined 21 patient-specific and socio-demographic parameters as well as 31 values of the Constant-Score with regard to their impact on patient satisfaction. Results In the univariable analysis higher patient satisfaction was correlated with higher age, private health insurance, light physical work, retirement, primary surgery, non-smoking, absence of chronic alcohol abuse, absence of peri- or postoperative complications, operation performed by the medical director as well as various Constant Score sub-values (p < 0.05). In the multivariable analysis absence of peri- or postoperative complications (p = 0.008), little postoperative pain (p = 0.0001), a large range of postoperative active abduction (p = 0.05) and a high postoperative subjective shoulder value (p = 0.0001) were identified as independent prognostic factors for high satisfaction. Conclusion After reconstructive shoulder surgery particular attention should be paid to prevention of complications, excellent perioperative pain control and restoration of abduction during rehabilitation. This study is first step towards a preoperative prediction model of a subjectively successful surgery as well as a tool to exclude irrelevant parameters in clinical routine

“Falar que não existe machismo... Claro que existe!”:: entrevista com Carola Saavedra

Entrevista com a escritora brasileira Carola Saavedra

“O Brasil é um país extremamente machista”:: entrevista com Luiz Ruffato

Entrevista com o escritor brasileiro Luiz Ruffato

“Há 200 anos era a mesma coisa”:: entrevista com Beatriz Bracher

Entrevista com a escritora brasileira Beatriz Bracher

“Sou um homossexual não praticante”:: entrevista com Marcelino Freire

Entrevista com o escritor brasileiro Marcelino Freire

“Nós somos machistas”:: entrevistas com escritores/as brasileiros/as

Este dossiê reúne seis conversas com escritores(as) brasileiros(as) levadas a cabo no âmbito da Feira do Livro de Frankfurt em 2013: Ana Paula Maia, Beatriz Bracher, Bernardo Ajzenberg, Carola Saavedra, Ferréz, Luiz Ruffato e Marcelino Freire. As primeiras questões das entrevistas centram-se em assuntos relacionados com os estudos de gênero, nomeadamente os diferentes conceitos de masculinidade(s) e feminilidade(s) na sociedade e na literatura brasileiras, partindo da teoria elaborada pela socióloga australiana R. W. Connell, uma das mais relevantes acadêmicas contemporâneas na área das masculinidades e das relações de gênero. Segue-se uma série de perguntas sobre as particularidades da obra de cada um(a) dos(as) escritores(as), as suas principais preocupações estéticas e as conexões com as obras dos(as) outros(as)

A sociedade aprendeu a cobrar do homem”:: entrevista com Ferréz

Entrevista com o escritor brasileiro Ferréz