Continuous Shots Research Articles

Investigation of Delay Jitter of Avalanche GaAs PCSS for Triggering High-Voltage Gas Switch

The delay jitter characteristics of gallium arsenide (GaAs) photoconductive semiconductor switches (PCSSs) triggered in avalanche mode were experimentally investigated under dc bias. In the dark-state measurement, the PCSS was tested under a 40-kV bias voltage to verify its withstanding voltage and reliability. In the ON-state measurement, the delay jitter time of PCSS at different triggering positions was measured. The experimental results showed that the shortest delay jitter time was obtained when the laser was applied to the middle position of the cathode electrode. To evaluate the long-time stability, the delay-jitter time was recorded after continuous shots. It shows an ascending trend in delay jitter time with the increase in operating shots. The degeneration of the delay jitter time of the PCSS was mainly attributed to the device damage, including electrode ablation and filament current ablation, which was verified by the analysis of scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Furthermore, a bipolar high-voltage gas switch integrated with PCSSs was successfully triggered by a low-energy fiber laser.

Numerical simulations for artillery barrel temperature variation considering mechanical friction heat under continuous shots

Accurate modeling of artillery barrel temperature distribution is important to evaluate thermochemical-mechanical erosion and thermal shock. For such heat conduction problems, the previous works ignore frictional heat, especially for continuous shots. To end this, this paper proposes a numerical simulation approach for the temperature field on the inner barrel wall considering the frictional temperature rise. In the novel scheme, the frictional temperature between the barrel and the rotating band is derived from the frictional heat theory, and the heat transfer model is computed coupling the interior ballistic codes with the finite difference method. A close-formed solution for the continuous shots with an incomplete cooling barrel is provided, and followed by a finite element numerical simulation. The good agreement between the aforementioned two simulations demonstrates a good accuracy of the developed solution form. The results show that there is a temperature peak at the initial part of the rifling, which is much higher than the other parts, and far exceeds the critical phase transition temperature of the barrel steel material.

Investigation on operational stability of a pulsed plasma thruster with a pressure probe

The Pulsed Plasma Thruster (PPT) was the first electric propulsion device to be implemented on a spacecraft in orbit (Zond 2) in 1964. However, the pulse ignition mode and the shot-to-shot discharge differences introduce challenges into the evaluation of the performance of PPTs. This work performs impact pressure measurements on a coaxial PPT (Pulsed Electric ThRuster of the University of Stuttgart, PETRUS) using a pressure probe. It is aimed to examine two specific thruster performance values that conventional thrust stands cannot easily obtain: the transient behavior during the phase where the final propellant surface contour is established (i.e., the shot-to-shot difference for the impulse bit during this phase) and the initial operation stability for the lifetime test. The impact pressure difference was measured at various discharge voltages using the pressure probe. To test the thruster's operational stability, a 5000 shots burn-in experiment was conducted on PETRUS. During the operation, the impulse bit variations were measured over 5000 continuous shots using the pressure probe. From the results, the impulse bit curve of PETRUS first shows a trend of decreasing impulse bit (the initial several hundred shots) and then an increasing trend (after 300 shots). After 2151 shots, the thruster's operating condition reaches a steady state with an impulse bit of 144 μN s. Additionally, the reliability of the pressure probe measurement is also evaluated by comparing the results with those from a thrust stand. The results are in good agreement at higher discharge voltages (from 0.9 kV to 1.6 kV), the maximum measured impulse bit difference of the pressure probe over the thrust stand is 9.7%. These results provide a dynamic evaluation of the thruster's operational stability from an engineering aspect. Correspondingly, the comparison results between the pressure probe and thrust stand is a preliminary verification of the pressure probe impulse bit measurement method in this work.

Mobile photo recommendation system of continuous shots based on aesthetic ranking

Abstract Image aesthetics have been a popular topic in the recent years. The users can obtain aesthetic score of any image by using the computational approaches based on photography rules. However, most approaches consider the task as an off-line process because those methods usually require high computational complexity. On the other hand, mobile devices (tablet and smart phone) have become an indispensable tool in our daily life. Many users are more willing to take photos with them instead of digital cameras. Thus, developing practical camera applications (APPs) for mobile devices has high application potential. In this paper, respect to the issue of hardware computation limitation of mobile devices, we first design an instant photo aesthetics evaluation method. It adopts several simple and effective features to predict photo scores. The preliminary results conducted on benchmark datasets verify its performance and efficiency. Based on this achievement, we develop a continuous-shot photo recommendation system. It includes two steps: dominant photo selection performed in partially-decoded compression domain and instant photo aesthetics ranking. The system can automatically list the photos with higher scores, and help users to select desired ones. Crowd sourcing tests are employed to evaluate system performance, which show that our system is effective for instant aesthetic rating and photo recommendation. 1

The Dynamic Performance and Thermal Computation of Electromagnetic Rail Launcher Considering Parameters Variation

For the electromagnetic rail launcher, the parameters variation has obvious effect on the dynamic performance and efficiency. This paper constructs the system simulation model of the electromagnetic rail launcher by using of Simulink software, and then analyzes the influences on the system dynamic performance for main devices. Based on the parameters and large current condition, the launching efficiency model is constructed, and the energy distribution characteristics are obtained. The loss of rail, armature, and feeder equipment is 38.7%, and the loss of arc extinguishing equipment is about 4.76%, so the heat loss is about 43.46% of total loss. When considering that the other loss is 33.37%, the system energy efficiency is 23.17%. Based on the design of the small prototype, the energy loss characteristics of the full prototype in launch rail and its temperature features are discussed in detail. The peak temperature is 276 °C after 11 continuous shots with converting coefficient being 5000 W/( $\text{m}^{{{2}}}\cdot \text {K}$ ), and it can decrease 58 °C if the better convection boundary condition is achieved, which means the rail can meet the requirement of the thermal management.

Proposal of a numerical model using the finite element analysis of pilger rolling for improvement of computation precision and efficiency

Abstract This paper presents a new numerical analysis method for cold pilger rolling which leads to compatible improvement of analysis accuracy and shortening calculation time. In pilger rolling, a raw tube is rolled by dozens of “shots”, which is repetitive reciprocating movement of caliber rolls. Previous studies carried out only one shot analysis for shortening calculation time. However, these studies cannot consider an accumulated plastic strain by the dozens of “shots”. The proposed method is composed of two models. In the first preliminary model, the accumulated plastic strain is evaluated based on the strain increment between the two continuous shots. The second main model is given the pre-strain calculated by the preliminary model, and analyses of shots are conducted until tool load becomes stable. This paper clarified the number of shots until stable tool load was obtained in the proposed model. In addition, the proposed model can improve analysis accuracy of the rolling load while shortening calculation time by 60 %, compared with the conventional models of dozen of shots.

Dynamics of Laser Triggered, Gas-Insulated Spark Gaps During Repetitive Operation

The Electra pulsed power system at the U.S. Naval Research Laboratory uses laser triggered SF6 gas-insulated spark gaps to transfer energy to a high power electron beam diode. These 1-MV spark gaps have a charge transfer of 10 mC per shot operating at 5 pules per second (pps) utilizing electrodes with the potential durability of 300 000 pulses. During continuous repetitive switch operation, after a few thousand shots intermittent nonfire events occur with greater frequency approaching 100 000 shots. The nonfire events and the lack of reproducibility and reliability reduce the potential applications for laser triggered spark gaps. Therefore, the temporal evolution and the spatial evolution of the switch dynamics have been examined. Gated camera images, streak camera images, and interferometry are used to characterize the dynamics of single shots to directly compare to the dynamics during continuous operation. The streak camera images indicate that the switch dynamics are dependent on the repetition rate. For single shots and 1 pps operation (9000 continuous shots), no misfires (mistimings or nonfires) are observed in the switch. This observation is concomitant with a consistent and reproducible breakdown position and breakdown dynamics. At 5 pps, the variations in the laser breakdown position (preferentially toward cathode) and the laser breakdown emission intensity are observed. After several thousands of continuous shots, nonfire events are detected in small groups, before normal operation resumes. A temperature differential of at least 22.2 K (40 F) between the SF6 gas at the top of the housing and the bottom of the spark gap housing is observed. The onset of nonfire events is correlated with the hydrodynamic changes, from increased temperature, of the SF6 gas flow within the spark gap. A redesign of the spark gap along with adequate cooling to reduce the hydrodynamic flow and forces of the insulating SF6 gas would mitigate if not eliminate nonfire events.

Buñuel’s social close-up: An entomological gaze on El ángel exterminador/The Exterminating Angel (1962)

Abstract This article proposes a new interpretation of Buñuel’s film-making strategies by examining his training in entomology and his early theorization of the Griffithian close-up as a technique whereby edited film-making can be made to conceive in a way that simple images or continuous shots cannot. This technique, I argue, implies the opposite of Auerbach´s unipersonal subjectivism in modernist literature, requiring a cinematic multipersonal subjectivism that is covalent with Bakhtinian dialogism. In developing his multi-personal subjectivism into a rational tool for opening a window on the irrational world of the unconscious, I believe Buñuel´s entomological training led him to conceive and represent a dialogical parasitism, similar to the posthumanist philosophy of Michel Serres decades later, as being inherent in all human relationships, a view most clearly conveyed in El ángel exterminador/The Exterminating Angel (1962).

サーモグラフィの連写画像の合成に基づくハイポイドギヤのかみ合いモニターと熱回路網モデルに基づく歯面の温度予測

サーモグラフィの連写画像の合成に基づくハイポイドギヤのかみ合いモニターと熱回路網モデルに基づく歯面の温度予測

Generation and measurement of complex laser pulse shapes in the SG-III laser facility

The generation and measurement of complex ultraviolet laser pulse shapes is demonstrated in the SG-III laser facility. Relatively high contrast ratio of 300∶1 required by the physics experiment is achieved and successfully measured. Two continuous main shots validate the reproduction and the stability of the pulse shape, which provide solid foundation for precise physics experiment and laser power balance.

Ranking highlight level of movie clips: A template based adaptive kernel SVM method

This paper looks into a new direction in movie clips analysis – model based ranking of highlight level. A movie clip, containing a short story, is composed of several continuous shots, which is much simpler than the whole movie. As a result, clip based analysis provides a feasible way for movie analysis and interpretation. In this paper, clip-based ranking of highlight level is proposed, where the challenging problem in detecting and recognizing events within clips is not required. Due to the lack of publicly available datasets, we firstly construct a database of movie clips, where each clip is associated with manually derived highlight level as ground truth. From each clip a number of effective visual cues are then extracted. To bridge the gap between low-level features and highlight level semantics, a holistic method of highlight ranking model is introduced. According to the distance between testing clips and selected templates, appropriate kernel function of support vector machine (SVM) is adaptively selected. Promising results are reported in automatic ranking of movie highlight levels.

Temperature Field and Thermal Stress Analysis of Large Caliber Gun Barrel

In order to analyze the temperature fields, temperature grads, thermal stress and thermal strain of large caliber machine gun barrel during firing, an analysis model was established for large caliber machine gun. The finite element analyze model are founded and the boundary condition of the model are loaded. The results indicated the temperature, temperature grads, thermal stress and thermal strain of the large caliber gun tube during continuous shots. The effect of thermal pulse loading on thermal stress, thermal strain is very obviously. So, thermal pulse loading is the primary origin of thermal stress, thermal strain of the large caliber machine gun barrel. At the same time, the thermal pulse loading is one of the important factors affecting the life of the gun tube.

Residual Stress Study of Autofrettaged Barrel under Impulsive Loading

An analysis model of barrel was established for rapid-firing gun by using the thermal structure direct coupling analysis method. As a solving tactics, finite element method was employed to analyze the influence of degree of autofrettage on the residual stress of the tube under impact load caused by high temperature and high pressure powder gases during continuous shots process. The results indicated that there is a significant effect of degree of autofrettage on the residual stress distribution of barrel. As the autofrettage level increases, the radius of the compressive tangential plastic strain zone on the inner wall and the maximal residual stress of the base near chromium-steel interface become larger. This is the cause that the tensile tangential plastic strain in the self-reinforced barrel easily occurred in the process of continuous shots after cooling. This goes against stability of the stress condition of the gun tube.

Low jitter, high voltage, repetitive laser triggered gas switches

The Electra pulsed power system at the Naval Research Laboratory is capable of supplying 16 kJ to a low impedance load within 140 ns, and it allows continuous operation of up to 5 pulses per second for several hours. Four laser triggered SF6 gas switches transfer the stored pulse forming line energy to the load. Each switch has a hold-off voltage of more than 1 MV and transfers a charge of 10 mC per shot. This paper describes the redesign of the gas switch with hemispherical electrodes to a flat electrode configuration, which led to an improvement in switch reliability. A one sigma switch jitter of ±1.2 ns has been achieved for tens of thousands of continuous shots, with an electrode erosion rate as low as 1 mg/C. Detailed statistical analyses are provided when the switches are operated at a SF6 pressure of 0.36 - 0.69 MPa, with a laser trigger energy of 1 - 18 mJ at 266 nm, and a switch hold-off voltage ranging from 0.7 - 1.2 MV.

Fractional sodium excretion and its relation to in-hospital morbidity and mortality in patients admitted with decompensated heart failure

Abstract Introduction, aim In general, failure to decrease the extracellular fluid volume despite liberal use of diuretics is often termed diuretic resistance. We aimed to correlate between urinary fractional sodium excretion as a marker of diuretic resistance in patients admitted with congestive heart failure and its impact on length of hospital stay together with in-hospital morbidity and mortality. Patients and methods 46 decompensated heart failure patients were enrolled in this study. We decided that the urine sample from which we can calculate the FENa level will be a 24-hour sample in an attempt to decrease the variability of FENa levels. FENa = 100 × Na ( urinary ) × creatinine ( plasma ) / Na ( plasma ) × creatinine ( urinary ) Intravenous furosemide was started on admission either as a continuous infusion or shots. It was followed-up during the hospital stay for inhospital mortality and morbidity. Results FENa results came out with a median value of 1.5% with minimum and maximum FENa results equal to 0.05% and 5.2%, respectively. The only three variables that contributed significantly to the prediction of hospital stay were Hb, LVEF, and FENa; with the latter variable showing the most significant relation. Conclusion, recommendation FENa can be used upon patient’s admission to guide therapy of heart failure in an attempt to reduce the hospital stay.

Giant optical limiting effect in Ormosil gel glasses doped with graphene oxide materials

Graphene materials have attracted interest in the field of optical limiting because of their outstanding linear and nonlinear optical (NLO) properties. However, poor solubility and agglomeration have limited the practical applications of these materials. Here, hydrophilic graphene oxide materials, including graphene oxide nanosheets (GONSs) and graphene oxide nanoribbons (GONRs) are synthesized. Using a facile sol–gel process, GONSs and GONRs are introduced into a methyltriethoxysilane modified silicate (Ormosil) glass matrix. NLO and optical limiting (OL) properties are investigated using a nanosecond Z-scan technique at 532 nm. Large OL effects of Ormosil hybrid glasses are revealed, whose optical limiting thresholds (Fth = ∼0.03 J cm−2) surpass those of corresponding suspensions by a factor of 5–20. We deduce that this behavior is mostly attributed to the combined mechanisms of nonlinear scattering and nonlinear absorption. The hybrid glasses are free of damage after hundreds of continuous laser shots with an energy of 800 μJ. These results indicate that Ormosil hybrid glasses doped with graphene oxide materials could be promising candidates for optical limiters.

A temporal context model for boosting video annotation

In this paper, we propose a new method to model the temporal context for boosting video annotation accuracy. The motivation of our idea mainly comes from the fact that temporally continuous shots in video are generally with relevant content, so that the performance of video annotation could be comparably boosted by mining the temporal dependency between shots in video. Based on this consideration, we propose a temporal context model to mine the redundant information between shots. By connecting our model with conditional random field and borrowing the learning and inference approaches from it, we could obtain the refined probability of a concept occurring in the shot, which is the leverage of temporal context information and initial output of video annotation. Comparing with existing methods for temporal context mining of video annotation, our model could capture different kinds of shot dependency more accurately to improve the video annotation performance. Furthermore, our model is relatively simple and efficient, which is important for the applications which have large scale data to process. Extensive experimental results on the widely used TRECVID datasets exhibit the effectiveness of our method for improving video annotation accuracy.

Step and Repeat Ultraviolet Nanoimprinting under Pentafluoropropane Gas Ambient

In the UV nanoimprinting process an antisticking layer such as fluorinated self-assembled monolayer (F-SAM) is grafted on the mold surface to diminish the demolding impact. These layers are supposed to deteriorate as the imprint steps mount up, resulting in defects in the cured resist layer. In this work, continuous multiple shots of UV nanoimprint were conducted in the air and in pentafluoropropane (PFP) gas environment and demolding forces in every imprint step were determined. The experiments revealed that the demolding forces for the imprint in PFP atmosphere drastically reduced compared with those in the air. Water contact angles of the mold surface were also determined in every 225 imprint steps to observe the degree of degradation of the antisticking layer. It was found that the antisticking layer was less damaged or contaminated in the PFP environment than it was in the air after a certain number of imprint steps.

The Politics and Practice of Voice: Representing American Sign Language on the Screen in Two Recent Television Crime Dramas

The Politics and Practice of Voice: Representing American Sign Language on the Screen in Two Recent Television Crime Dramas

216 回転支持平板の衝突跳ね返り運動の抑制(衝突減少・衝突振動,OS-1 振動基礎,総合テーマ「伝統を,未来へ!」)

When we take pictures with continuous shots with single lens reflex camera, the inner mirror must repeats to go down and up with very high-speed. In this operation, the mirror hits to a stopper and rebound instantaneously. We investigate the rebound characteristics of the mirror model with free fall testing. Rebound angle of the model is varying by the stopper position. In the experiments, we find the stopper position which has lower amount of rebound angle. And the experimental modal analysis is carried out for the mirror model.