Converging Proton Minibeams with Magnetic Fields for Optimized Radiation Therapy: A Proof of Concept

Proton MiniBeam Radiation Therapy (pMBRT) is a novel strategy that combines the benefits of minibeam radiation therapy with the more precise ballistics of protons to further optimize the dose distribution and reduce radiation side effects. The aim of this study is to investigate possible strategies to couple pMBRT with dipole magnetic fields to generate a converging minibeam pattern and increase the center-to-center distance between minibeams. Magnetic field optimization was performed so as to obtain the same transverse dose profile at the Bragg peak position as in a reference configuration with no magnetic field. Monte Carlo simulations reproducing realistic pencil beam scanning settings were used to compute the dose in a water phantom. We analyzed different minibeam generation techniques, such as the use of a static multislit collimator or a dynamic aperture, and different magnetic field positions, i.e., before or within the water phantom. The best results were obtained using a dynamic aperture coupled with a magnetic field within the water phantom. For a center-to-center distance increase from 4 mm to 6 mm, we obtained an increase of peak-to-valley dose ratio and decrease of valley dose above 50%. The results indicate that magnetic fields can be effectively used to improve the spatial modulation at shallow depth for enhanced healthy tissue sparing.

Forecasting process parameters on weld nugget hardness of filler added friction stir welded dissimilar aluminium alloys 5052 And 6082 joints

This article deals with the optimization of friction stir welding process parameters with filler ratios on dissimilar Aluminium alloy groups. For this purpose, 6 series Aluminium alloy 6082 and 5 series Aluminium alloy 5052 were taken. Microhardness property was conducted under various rotational speeds, welding speed, plunge depth, Center distance between the holes and filler mixing ratio. The Central Composite Design (CCD), the most commonly used Response Surface Methodology (RSM), is considered to develop the prediction equation. A validation analysis is carried out, and the results were compared with the relative impact of input parameters on weld nugget microhardness. It is observed that the increase in welding speed with plunge depth and filler ratio result in the increase of weld nugget microhardness up to a maximum value. The maximum weld nugget hardness of fabricated joint was obtained with the welding process parameters combination of 1000 rpm rotational speed, 125 mm/min welding speed, 0.15 mm plunge depth, 2 mm centre distance between the holes, and filler ratio of 95% Mg and 5% Cr.

КІНЕТОСТАТИЧНЕ ДОСЛІДЖЕННЯ ШАРНІРНИХ ПРОСТОРОВИХ МЕХАНІЗМІВ ГАЛТУВАЛЬНИХ МАШИН (ЧАСТИНА 1: ДОСЛІДЖЕННЯ МЕХАНІЗМУ З ДОДАТКОВОЮ РУХОМОЮ ЛАНКОЮ – КОРОМИСЛОМ)

Kinetostatic study of a statically determined hinged spatial mechanism without redundant (passive) connection with an additional movable link – a rocker arm of a machine for processing parts, in which the working container performs complex spatial movement. Methodology. The essence of the kinetostatic research was to determine the radial and axial components of the reactions in all rotational kinematic pairs of the hinged statically defined spatial mechanism of the machine for processing parts, when it is idling. The kinetostatic study was implemented using the SolidWorks 2016 computer-aided design system with preliminary 3D modeling of this machine design with an additional moving link – a rocker. Results. In the course of the kinetostatic study, 3D modeling of a machine with an additional movable link – a rocker arm in the SolidWorks 2016 computer-aided design system was carried out, the maximum values of the radial and axial components of reactions in all rotational kinematic pairs of the machine for processing parts were determined, the effect of changing the center distance of the intermediate connecting rod (working capacity ) on the increase in the maximum values of the reactions in all rotational kinematic pairs. Scientific novelty. The relationship between the center distance of the intermediate connecting rod (working capacity) and the change in the maximum values of the reactions in all rotational kinematic pairs of the machine for processing parts is determined. As a result, it becomes possible to determine the maximum permissible center distance of the intermediate connecting rod to ensure the durable operation of the machine. Practical significance. It is determined that the nature of the change in the maximum values of the radial and axial components of the reactions in each rotational kinematic pair of the spatial mechanism depends on the value of the coefficient characterizing the ratio of the center-to-center length of the intermediate connecting rod (working capacity) to the center-to-center length of the driving or driven connecting rods of the machine. The range of variation of this coefficient has been determined, within which it is rational to design this machine design. The results obtained can be used in the corresponding design bureaus of machine-building enterprises at the stage of designing tumbling equipment with a complex spatial movement of working containers.

Abstract 12497: Long Transport Distances to a Tertiary Cardiac Arrest Center Does Not Affect Survival in Patients With Out-of-Hospital Cardiac Arrest

Introduction: Patients with out-of-hospital cardiac arrest (OHCA) are increasingly transported to tertiary cardiac arrest centers, when the arrest is presumed to be of cardiac origin. For some patients, centralization has led to longer transport distances to advanced care resulting in prolonged prehospital system delays, which may affect outcome. Hypothesis: Longer transport distance to center for patients with OHCA reduces 30-day survival. Methods: Central Denmark Region covers rural and urban areas of 13 000 square kilometers and has a population of approximately 1.3 million inhabitants. Aarhus University Hospital functions as the tertiary cardiac care hospital with access to 24/7 cardiac catherization service and extracorporeal cardiopulmonary resuscitation. Distance to center varies greatly among citizens in the region; with longest distance exceeding 170 km. This observational retrospective study included all patients with OHCA referred to Aarhus University Hospital from 2015 to 2018. Kaplan-Meier curves were conducted to evaluate association between distance and mortality. The odds of 30-day mortality were generated using logistic regression. Results: A total of 807 patients with OHCA were referred to center. Distance to center was < 25km (22%), 25 to 50km (40%), 50 to 100km (20%) and > 100km (18%), respectively. The median prehospital system delay from collapse to arrival at center was 70 minutes [IQR, 55-90 minutes]. Logistic regression did not demonstrate an association between 30-day mortality and increasing distance to center (distance < 25 km as reference, 25 to 50km: OR 0.83, 95% CI [0.58-1.20], 50 to 100km: OR 0.96, 95% CI [0.62-1.47] and >100km: OR 1.20, 95% CI [0.77-1.88]). Conclusions: In OHCA patients with long transport distances to a tertiary cardiac center, survival was similar in patients with short distance to center. Centralization of post cardiac care is feasible in the setting of long transport distances.

Deteksi Gulma Berdasarkan Warna HSV dan Fitur Bentuk Menggunakan Jaringan Syaraf Tiruan

<p class="Abstrak">Gulma merupakan tanaman pengganggu dalam lahan pertanian. Herbisida merupakan obat yang efektif membunuh gulma tersebut. Penyemprotan herbisida harus tepat sasaran kepada gulma saja dan tidak mengenai tanaman. Penelitian ini membuat sistem yang dapat mendeteksi gulma secara otomatis di antara tanaman pada lahan pertanian riil. Sistem ini menggunakan gambar lahan pertanian riil dimana tanaman tampak utuh (daun dapat lebih dari satu) yang diambil menggunakan kamera dengan posisi vertikal menghadap ke bawah. Algoritma yang dibuat menggunakan segmentasi berdasarkan warna hijau dalam ruang warna HSV untuk mendeteksi daun, baik gulma maupun tanaman pada beragam pencahayaan. Sebanyak tiga fitur bentuk domain spasial digunakan untuk membedakan gulma dengan tanaman yang memiliki karakteristik bentuk daun yang berbeda. Fitur bentuk yang digunakan adalah <em>Rectangularity, Edge-to-Center distances function</em>, dan <em>Distance Transform function</em>. Klasifikasi gulma dan tanaman menggunakan metode Jaringan syaraf tiruan (JST) yang dapat dilatih secara <em>offline. </em>Dari 149 tanaman yang terdeteksi dimana 70% sebagai data training, 15% data validasi dan 15% data uji, didapati akurasi pengujian sebesar 95.46%.</p><p class="Abstrak"><em><strong><br /></strong></em></p><p class="Abstrak"><em><strong>Abstract</strong></em></p><p class="Abstract"><em>Weed is a major challenge in a crop plantation. A herbicide is the most effective substance to kill this unwanted vegetation. Spraying the herbicide must be done carefully to target the weeds only. Here in this research, we develop an algorithm that detects weeds among the plants based on the shape of their leaves. The detection is based on images that were acquired using a camera. The leaves of weeds and plants were detected based on their green color using segmentation in HSV color-space as it is more effective to detect objects in various illumination. Three shape features were extracted, which are Rectangularity that is based on Rectangularity, Edge-to-Center distance function, and Distance Transform function. Those features were fed into a learning algorithm, Artificial Neural Network (ANN), to classify whether it is the plant or the weed. The testing on the weed classification in a real outdoor environment showed 95.46% accuracy using a total of 149 detected plants (70% as training data, 15% as validation data, and 15% as testing data).<strong></strong></em></p><p class="Abstrak"><em><strong><br /></strong></em></p>

Chord Mu (µ) and Chord Alpha (α) Length Changes in Fuchs Endothelial Corneal Dystrophy before and after Descemet Membrane Endothelial Keratoplasty (DMEK) Surgery

This paper will evaluate chord mu and alpha length in patients with Fuchs endothelial corneal dystrophy (FECD) and its changes following Descemet membrane endothelial keratoplasty (DMEK). Patients with FECD that underwent DMEK surgery were included in this retrospective study. Scheimpflug Tomography was carried out in order to calculate chord mu and chord alpha lengths prior to surgery and at 3 and 12 months postoperative. This study included 27 eyes from 27 patients. Significant changes in chord mu were observed within the first three months (from 0.47 ± 0.32 to 0.29 ± 0.21 mm, p < 0.01) and remained stable 12 months postoperative (0.30 ± 0.21 mm, p > 0.05). However, chord alpha remained stable throughout the 12 months post surgery (from 0.53 ± 0.19 to 0.49 ± 0.14 mm, p > 0.05). In addition to the pupillary center distance from the corneal apex (from 0.35 ± 0.25 to 0.34 ± 0.20 mm, p > 0.05) also remain stable. In FECD patients undergoing DMEK surgery, chord mu length decreased, and chord alpha length remained stable after 12 months of follow-up.

A Hydraulic Soft Microhand with an Application of Live Insect Manipulation

We have developed micro scale hydraulic/pneumatic soft grippers and demonstrated the handling of an insect. These grippers are built on Polydimethylsiloxane (PDMS) with the soft material casting technique to form three finger-like columns, which are placed on a circular membrane. The fingers have a length of 1.5mm/2mm and a diameter of 300µm each; the distance between two fingers is 600µm of center-to-center distance. Membrane is built as a 150µm soft skin on the top of a cylindrical void. Applying a pressure difference between the interior of the void and the exterior can bend the membrane. Bending the membrane causes the motion of opening/closing of the gripper, and as a result, the three fingers can grip an object or release it. The PDMS was characterized and the experimental results were used later in Abaqus software to simulate the gripping motion. The produced force and range of deformation of the grippers were investigated by simulation and experiment. The results of the simulation agrees with the experiments. The maximum 543 µN force was measured for the microfluidic compatible microgrippers.Using this microhand gripper, the an ant was manipulated successfully without any damage. Results showed fabricated devices have great potential as a micro/bio manipulator.

Experimental and Numerical Study on the Flow Ripple of Circular-arc Gear Pumps Considering the Center Distance Deviation

Novel circular-arc gear pumps effectively solve the problems of oil trapping and flow pulsation experienced with traditional gear pumps. However, the center distance deviation associated with assembly and installation during gear pump processing has an important influence on the outlet pressure pulsation characteristics of circular-arc gear pumps. First, the circular-arc tooth profile equation, conjugate curve equation and meshing line equation were derived to design the circular-arc gear meshing and center distance deviation functions. Second, the circular-arc gear tooth profile was accurately obtained. Then, a pressure pulsation characteristic simulation model for the novel circular-arc gear pumps considering the center distance deviation was established. The results show that with the increase of center distance deviation, the outlet flow rate of the arc gear pump increases first and then decreases greatly. Moreover, the center distance deviation has little effect on the independent tooth cavity pressure. Finally, the proposed fluid dynamic model is used to simulate a commercial circular-arc gear pump, which was tested within this research for modeling validation purposes. The comparisons highlight the validity of the proposed simulation approach.

A New Analytical Method for Modeling the Effect of Assembly Errors on a Motor-Gearbox System

The well-known gear tooth defects such as root cracks and flank spalls have been widely investigated in previous studies to model their effects on the time varying mesh stiffness (TVMS) and consequently the dynamic response of motor-gearbox systems. Nevertheless, the effect of assembly errors such as the center distance and the eccentricity has been less considered in past works. Determining the signature of these errors on the system response can help for their early detection and diagnostic to avoid overloading and failure of gears. An original geometric-based method combined with the potential energy method is proposed in this paper to accurately model the effect of these assembly errors on the TVMS of mating spur gear pairs. This is achieved by updating the line of action equation (LOA) at each meshing step using the actual coordinates of gear centers and employing a contact detection algorithm (CDA) to determine the actual contact points coordinates. An electrical model of a three-phase induction machine was then coupled with a dynamic model of a one-stage spur gear system to simulate the effect of assembly errors on the electromechanical response of the motor-gearbox system. The simulation results showed that the center distance error induces a reduction in the TVMS magnitude and the contact ratio, whereas the eccentricity error causes a double modulation of the TVMS magnitude and frequency. In addition, the results showed that assembly errors can be detected and diagnosed by analyzing the system vibration and the motor phase-current.