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In order to solve the problem of quality degradation of underwater image due to absorption and scattering of water body, this paper proposes a method of underwater image enhancement based on the combination of computational imaging and deep learning. The method has achieved good results in removing image blur and scattering noise. It can effectively enhance the target images in turbid water, which will allow underwater image applications to have a wider range of areas.

Compared with images taken in the air, underwater images are susceptible due to the adverse effects of complex water conditions, such as absorption, attenuation, scattering, various noises, and uneven lighting, etc. These effects severely reduce the quality of underwater imaging and give rise to many problems among which is image color distortion. To fully acknowledge the underwater scenes, it is important to acquire the images with accurate colors, especially for marine rescue, underwater target recognition, and marine ecological research. To address this problem, this paper proposes an underwater imaging technology based on a light field camera array. The application of this technology can not only perform accurate color correction processing on the captured images but also expand the dynamic range of underwater images, thereby obtain enhanced high-quality, true-color underwater images. The experimental system in this paper contains a 3*3 camera array that simultaneously captures images of underwater targets with different exposure times. As the light attenuation coefficient of different wavelengths in water varies with the wavelength, during the color restoration process, we measure the relative value of the underwater spectral power distribution concerning the air, calculate the tristimulus value change according to the colorimetric principle, and convert the tristimulus value change in the CIEXYZ color space to the CIE La*b* color space. The color on the underwater images obtained by the camera array is then compensated. Then, in the image fusion process, images with different exposure are used to recover the response function of the imaging process, and multiple images are fused into a single, high-dynamic-range radiance map using high quality tone mapping technique in the radiance value dynamic display high-contrast images on devices with limited range. Experimental results show that our light-field imaging color correction and dynamic range expansion processing methods have obvious advantages over single cameras in underwater color correction and underwater moving target imaging detection, which provide advanced technology and equipment for underwater in-situ applications.

Background Idiopathic pulmonary fibrosis is a lethal fibrosing interstitial pneumonia characterized by progressive worsening of dyspnea and lung function with poor prognosis. Since pirfenidone was approved for IPF treatment, the search for more effective candidates has been greatly intensified. Methods In this study, the antifibrotic effects and mechanisms of compound PBD-617 , the ideal candidate discovered in our previous work, were investigated on transforming growth factor-β1 (TGF-β1)-induced human embryonic lung fibroblasts (HELF) and on bleomycin (BLM)-induced pulmonary fibrotic rats. Results Oral administration with PBD-617 decreased the levels of collagen I, collagen III and matrix metalloproteinase 7 , and inhibited the protein expression of α-smooth muscle actin in BLM-induced pulmonary fibrosis rats. Furthermore, PBD-617 suppressed the expression of TGF-β1 , phosphorylated Smad3, phosphorylated p38 and activator protein 1 on TGF-β1-induced HELF, while the regulation could be rescued by using p38 agonist p79350. Conclusion PBD-617 not only inhibited TGF-β1-induced HELF proliferation, but also attenuated BLM-induced pulmonary fibrosis in rats, with efficacy to some extent higher than that of pirfenidone at the same effective dosage. PBD-617 attenuated pulmonary fibrosis effectively by suppressing activation of TGF-β1/Smad3 and p38 signaling pathways .

The teaching methods of vocational college teachers can not only reflect the comprehensive quality and professional level of teachers, but also highlight the innovative ability of teachers. Good teaching methods can not only help students learn professional knowledge, but also affect students' professional employment development. This article analyzes the teaching methods of vocational college teachers under the background of big data.

Based on the wavefront aberration theory and the coordinates transform, the free form optical induced aberration’s characteristic of optical system has been analyses in this paper. The optical wavefront error and the free form surface can be express as Fringe Zernike polynomial; the free form optical on the surface (Stop or Entrance pupil or Exit pupil) affects all the field angles equally. If the surface is not the pupil of optical system, the aberration observed is different from the free form itself because the footprint of the beam for an off-axis field point only covers part of the surface. For the Fringe Zernike surface figure on a surface not at pupil, it will transform into lower order Fringe Zernike aberration in the optical system, the relationship between different Fringe Zernike aberration and field is different, and the location zero for the lower aberration always reside at the center of the field of view.

Cloud radio access network (C-RAN) is considered as a promising approach to solve the bandwidth crunch problem for future wireless network. Another important element for future network is sensors that can monitor physical or environmental conditions. Currently, most sensors need batteries for power, which is energy-consuming and maintenance-heavy. To further improve energy efficiency (EE) of sensors in C-RAN, this paper proposes a new structure as well as practical circuit design for green sensors in C-RAN. The structure can enable sensors to harvest energy from radio signals transmitted by neighbor remote radio heads (RRHs) and user terminals (UTs). To demonstrate the validity of the new structure, a practical circuit design is suggested and the corresponding hardware platform is realized. Specifically, selection criteria for electrical component parameters and design of an impedance-matching network are discussed in details. In addition, two methods to stabilize the output voltage are proposed and analyzed. Finally, simulation results as well as experimental results are provided to corroborate our proposed studies.

The decomposition of limestone in converter slag directly determines the speed of slag melting for lime that has a strong effect on the steelmaking process of the converter. In this paper, a high temperature furnace was used to study the decomposition behavior of cylindrical limestone samples in the converter early slag at the temperatures of 1250 °C, 1300 °C, and 1350 °C under laboratory conditions, and macro-dynamics equation was used to determine the rate-determining step for limestone decomposition in the converter early slag. The results show that when the limestone is decomposed in the early converter slag, the heat transfer from the slag through the lime layer to the unreacted core is the rate-determining step. The limestone decomposition rate in converter slag is slightly lower than that in hot metal. Finally, the suitable grain size of the limestone added into the converter was determined. Thus, this study provides theoretical guidelines for practical use of converter steelmaking in industrial production.

The advantage of Carbon Fiber Reinforced Polymer (CFRP) is obvious as a common space material for low density, low thermal expansion coefficient and high specific stiffness characteristics, it is the ideal material choice for space optical reflector. Mirror structure with honeycomb can achieve high rates of lightweight, as well as high specific stiffness. For Φ300mm CFRP mirror, accounting of the actual process properties of CFRP, mirror panels laminated based on thermal stability design, honeycomb fabricated using one innovative inlaying-grafting design method. Finally, lightweight structure design of the CFRP primary mirror completed, the thermal stability result of the Φ300mm CFRP mirror achieved is 10nm°C.

Through introducing transformed pupil vector and shifted center of aberration fields vector into the nodal aberration expansions of an axially symmetric optical system, the aberration expression in third order of an off-axis optical system and misaligned off-axis optical system are detailed. Nodal aberration characteristics of misaligned off-axis optical system are revealed only by analyzing the pupil decentration vector, aberration fields shifted vector and the aberration coefficients of the axially symmetric optical system. Actually, it is well demonstrated that the 3rd spherical aberration, 3rd coma, 3rd astigmatism in a misalignment off-axis system are comparable to the aberrations in a misalignment axially symmetric system. Otherwise it will not only induced constant 3rd spherical aberration but also constant 3rd coma and 3rd astigmatism over the field of view, when aligned an off-axis optical system elements with error axial spacing.

Computer-generated hologram (CGH) is an effective way to compensate wavefront aberration in null test of aspheric surfaces and freeform surfaces. Our strategies of CGH design for 600mm diameter SiC primary mirror surface figure testing are presented, and an experiment demonstrating the compensation test results of CGH is reported. We design a CGH including two sections on the same substrate in order to align the CGH to the incident wavefront: main section for compensating wavefront in null test, alignment section for adjusting the relative position between CGH and interferometer. In order to isolate different orders of diffraction, we used power carrier to make different orders of diffraction come to focus at different position along the axis to avoid ghost reflections. We measured the 600mm diameter SiC primary mirror using this CGH, and the surface test result is 0.033λ rms.

With the development of space optical technology,space camera is required to be characterized by both high resolution of ground sample distance and ability of multi-spectral imaging.Thus the optical system design must be satisfied with the demand of large field of view and small distortion.Based on the on-axis three-mirror-anastigmat system,a new type of optical system was designed,which is characterized by small central obscuration,low optical distortion and reasonable arrangement of panchromatic and multi-spectral CCD.The results indicate that the field angel reaches 1.6°,the system line central obscure coefficient is lower 1/3,the optical system distortion is less than 0.5%,MTF is superior to 0.47 at 50 lp/mm,the image quality reaches the limit of optical diffraction,when the focal length is 12 000 mm,focal ratio is 12,and the spectrum band is from 450 to 900 nm.So the proposed optical system can meet the demand of high resolution multi-spectral space cameras.

Study design Applying rotating rod techniques to reduce irreducible atlantoaxial dislocation. Objective To spare the occipital-C1 motion by the strategy in reduction of before surgery irreducible atlantoaxial dislocation with obvious neurologic symptoms and congenital odontoid aplasia. Summary of background data The treatment of atlantoaxial dislocation (AAD) is a challenging problem for most surgeons. Posterior surgical stabilization of C1 and C2 include C1-C2 transarticular screws, or C1 lateral with C2 pars screws. These constructs, however, are based on preoperative reductions. When preoperative skull reduction fails and myelopathic symptoms coexist, long-segment cervico-occipital fusion and decompression are usually the only practical choice. Methods The authors explored a different surgical technique to spare the axial occipital joints by rotating rods in polyaxial C1, C3 lateral mass, and C2 pars screws, functioning as a lever analogue. Three before surgery irreducible AAD cases with obvious neurologic symptoms and congenital odontoid aplasia were successfully reduced and fused with this procedure. The authors used intraoperative somatosensory-evoked potential monitoring and intraoperative fluoroscopy. Preoperative skull traction was employed to distract and help extend the atlantoaxial complexes. Results Three C1-C2 dislocations were reduced completely without any deterioration of neurologic signs. Cervical myelopathic symptoms recovered soon after the operation. No atlantoaxial subluxation recurred. They returned to their normal work and/or activities. Conclusion The rotating rod strategy is a viable option to reduce and fuse C1-C3 for AAD with odontoid aplasia. It spares the occipital-C1 motion.

Based on the principle of null lens,a new method of error-separation was proposed in null testing.A mathematic model was developed to separate misalignment-induced aberration from the test result.The method was used in the simulations of an off-axis aspheric mirror.The wavefront aberration induced by misalignment is 0.0026λRMS(λ=632.8 nm) after the alignment,compared with 0.2332λRMS before the alignment,which reflects that this method has high accuracy and can improve the efficiency of the null test.

Temperature filed distributing of a high resolution space telescope is analyzed by thermal-optical method based on optical front-wave-error theory,and thermal contral target is ascertained.The thermal tests in the vacuum are carried out to validate the analysis.Tests results indicate that the ideal focal plane position vs temperature level are linearity,and changes scope approximately 0.08～0.1 mm·℃-1.As the macrocosmic temperature changing within(20±1)℃,system MTF change about 0.02.When the temperature grads are more than 2 ℃ in axis direction and diameter direction,the ideal focal plane position departure happenes and the MTF decline obviously if unfocus.

With the development of space technology,small satellite will be widely applied.The paper design a catadioptric system base on Ritchey-Chretion system which including three sphere correction lens.The system has a focal length of 1000,F number of 5,and spectrum band of 450~900 nm,and the field angle reaches 2.3°.the result indicates that,MTF reaches 0.47 at 77 lp/mm with 15% central obscure,the quality of image approaches the diffraction limit,and optical system distortion is less than 0.5%.The system with simpler structure,small size and light weight,can be used in light-small satellite.

In order to improve the imaging quality of optical system, high precision surface of mirrors are put forward to improve their imaging quality. It makes their fabrication harder. Wavefront aberration induced by alignment is analyzed in off-axis parabolic mirror system based on the wavefront aberration theory. The surface error of off-axis parabolic mirror can be compensated by alignment so it will reduce the fabrication difficulty, shorten its period and save its cost. In the simulations of an off-axis parabolic mirror with surface error λ/40 RMS (λ=632.8 nm) ( Root Mean Squre) with ZEMAX software, the figure accuracy is under λ/40 RMS after alignment. It shows that surface error of off-axis parabolic mirrors could be compensated effectively by alignment.

During the GPS observation in minefield especially in open-pit, the differences between stations are usually large, so that the influence of survey error is different from that in other flat area, and hence the various GPS methods are applied in the detailed surveys according to the different demands and typical site. Based on the analysis of our testing data, the key factor affecting the result precision exists in the coordinate transformation, that is, in the transformation of WGS84 ellipsoidal coordinates to the local planimetric coordinates and geodetic height. Therefore, South Toolbox 4.0 software is applied in the coordinates transformation to compute a set of ideal local coordinate transforming parameters in some region where may be ascertain problem happened, and the state coordinates system is not be used. Aiming at the various sources of GPS static positioning, both of absolute and relative positioning methods are applied in testing the factors influencing the precision of GPS positioning in minefields, considering PDOP value and coordinates transformation, and hence some practical conclusions about the static relative positioning accuracy of GPS dual frequency receivers in minefields are put forward here.

An arbitrary three-phase shifting algorithm is introduced in order to achieve full range spectral optical coherence tomography imaging of biological tissue. Theoretical treatment behind this approach is given and experimentally verified. It is shown that this method is capable of eliminating the undesired auto-correlation and complex conjugate images, leading to the un-obscured full range spectral OCT imaging. An intact porcine eye is used to demonstrate the potential of such a method for biological imaging.

With the rapid development of the cloud computing, massive information is distributed in the structure "cloud storage", leading to the heterogeneous data sources, and the "lost phenomenon" may occur in the process of information retrieval. To solve this problem, this paper builds the heterogeneous data integration model in the cloud computing environment, which includes three layers and five function modules: data acquisition and analysis interface in the cloud, data organization task scheduling engine, and heterogeneous data integrated interface based on the ontology. Also, common technologies used in unified retrieval of heterogeneous data resources are presented in this paper, such as parallel retrieval technology, server cluster retrieval technology, webpage's deep mining technology and retrieval database sharing technology.

A two-phase shifting method is introduced to eliminate the strong autocorrelation noise inherent in spectral optical coherence tomography and to mitigate the unwanted auto- and cross-coherent terms introduced by the reflections from various optical interfaces present in the system. Furthermore, this method is also able to amplify the desired signal by a factor of 2. The feasibility of such a method is demonstrated using a mirror-like object. An intact porcine cornea tissue in vitro is also used to show the potential of this method for biological imaging.

This paper implements the optical filter fiber Bragg grating (FBG) sensor demodulation system based on the tunable Fabry-Polo (F-P) filter. Paper firstly introduces the FBG sensor demodulation system block diagram; Then we uses the Optisystem software to build a virtual system and set parameters and obtain the simulation result that the optical power with the frequency has a good linear relationship; Finally we makes experimental verification finding that Simulation results are consistent with the experimental results.

Determine the misalignment of optical element quickly and exactly is the key to the technology of computer-aided alignment (CAA). For alignment a three-mirror off-axis field bias system, the sensitivity matrix method was used to simulate the alignment process. The results of simulation show that the sensitivity matrix method was not convergence. A new CAA method to get misalignment was put forward; the misalignment was obtained by programming the function of optical design software CODE V’s auto-optimization option. The system’s alignment characteristic was analysis and made use of this new method put up a computer simulation. The results of simulation show that the misalignment determined by only once auto-optimization and guidable to alignment of this system. After alignment, the optical system produced a measured wave front error across the all image plane less than 0.08 waves RMS at λ=0.6328μm.

Single wavelength illumination is used in the traditional ptychography. Even though using multi-wavelength to improve image quality, it takes the scheme of illuminating in turn due to the requirement of coherence. So far, the addition of incoherent modes has been regarded as a nuisance in diffractive imaging. Here we propose a scheme of incoherent ptychography and an algorithm of information multiplexing that uses the multi-wavelength illumination simultaneously, which are demonstrated in experiment and simulation. Compared with the scheme of traditional ptychography, it can recover not only the object well, but also the spectral response of the object, probes of complex value and spectral weight of each wavelength respectively. This method obtains much information about the object and owns the multichannel and multispectral merits. Meanwhile, by means of color image coding, this method can retrieve true color images and enhance the image quality. The proposed algorithm has strong robustness. Besides, we also investigate how many modes can be recovered by this method. The work may open up possibilities for information multiplexing in ptychography and multispectral microscopy imaging over various applications.

Electroluminescence (EL) is observed from the Au/Si-rich SiO2 film/p-Si diodes, in which the Si-rich SiO2 films are scored deliberately by a diamond tip. The EL intensity of the scored diode annealed at 800 degreesC is about 6 times of that of the unscored counterpart. The EL spectrum of the unscored diode could be decomposed into two Gaussian luminescence bands with peaks at about 1.83 and 2.23eV, while for the EL spectrum of the scored diode, an additional Gaussian band at about 3.0eV appears, and the 1.83-eV peak increases significantly in intensity. The photoluminescence (PL) spectrum of an unscored Si-rich SiO2 film has only one band peaking at about 1.48eV, whereas the PL spectrum of the scored one has two bands at about 1.48 and 1.97eV. We consider that the high-density defect regions produced by the scoring provide new luminescence centres and become some types of nonradiative centres in the Si oxide layer, which thus result in changes of the EL and PL spectra.

Topical medication remains the first line treatment of glaucoma; however, sustained ocular drug delivery via topical administration is difficult to achieve. Most drugs have poor penetration due to the multiple physiological barriers of the eye and are rapidly cleared if applied topically. Currently, daily topical administration for lowering the intra-ocular pressure (IOP), has many limitations, such as poor patient compliance and ocular allergy from repeated drug administration. Poor compliance leads to suboptimal control of IOP and disease progression with eventual blindness. The delivery of drugs in a sustained manner could provide the patient with a more attractive alternative by providing optimal therapeutic dosing, with minimal local toxicity and inconvenience. To investigate this, we incorporated latanoprost into LUVs (large unilamellar vesicles) derived from the liposome of DPPC (di-palmitoyl-phosphatidyl-choline) by the film hydration technique. Relatively high amounts of drug could be incorporated into this vesicle, and the drug resides predominantly in the bilayer. Vesicle stability monitored by size measurement and DSC (differential scanning calorimetry) analysis showed that formulations with a drug/lipid mole ratio of about 10% have good physical stability during storage and release. This formulation demonstrated sustained release of latanoprost in vitro, and then tested for efficacy in 23 rabbits. Subconjunctival injection and topical eye drop administration of the latanoprost/liposomal formulation were compared with conventional daily administration of latanoprost eye drops. The IOP lowering effect with a single subconjunctival injection was shown to be sustained for up to 50 days, and the extent of IOP lowering was comparable to daily eye drop administration. Toxicity and localized inflammation were not observed in any treatment groups. We believe that this is the first demonstration, in vivo, of sustained delivery to the anterior segment of the eye that is safe and efficacious for 50 days.

Purpose: To determine the efficacy of a subconjunctival injection of hyaluronic acid (HA) with 5-fluorouracil (5FU) formulation as an adjunct in reviving bleb function by needling. Design: Prospective, randomized, controlled trial. Participants: Fifty patients with previous trabeculectomy and scheduled by the managing physician for a needling intervention. Methods: One eye of each patient was randomized to receive needling with HA-5FU mixture or needling with subconjunctival injection of 5FU solution alone. Main Outcome Measures: The primary outcome was the percentage of subjects with an intraocular pressure (IOP)

With the thermal effects of substrate and package in mind, electrothermal simulations are performed on the transient response of transistors under the injection of electromagnetic pulses by adopting the 2-D device simulator ISE-TCAD. Simulation results show that the junction temperature inside a transistor will increase so instantly to the melting point of silicon within tens or hundreds of nanoseconds as to damage the device when the current mode second breakdown arises in the transistor for electromagnetic pulses with high power. In this case, the thermal resistance of package has little influence over the burnout time and damage energy. However, when the electromagnetic pulse has too small a power to produce the current mode second breakdown, the thermal mode second breakdown will arise in the transistor. In this case, the thermal resistance of package will have a notable effect over the burnout time and damage energy.

Background: This study demonstrates a critical role in CNS innate immunity of the microglial Toll-like receptor 4 (TLR4) in the induction and maintenance of behavioral hypersensitivity in a rat model of bone cancer pain with the technique of RNA interference (RNAi). We hypothesized that after intramedullary injection of Walker 256 cells (a breast cancer cell line) into the tibia, CNS neuroimmune activation and subsequent cytokine expression are triggered by the stimulation of microglial membrane-bound TLR4. Results: We assessed tactile allodynia and spontaneous pain in female Sprague-Dawley (SD) rats after intramedullary injection of Walker 256 cells into the tibia. In a complementary study, TLR4 small interfering RNA (siRNA) was administered intrathecally to bone cancer pain rats to reduce the expression of spinal TLR4. The bone cancer pain rats treated with TLR4 siRNA displayed significantly attenuated behavioral hypersensitivity and decreased expression of spinal microglial markers and proinflammatory cytokines compared with controls. Only intrathecal injection of TRL4 siRNA at post-inoculation day 4 could prevent initial development of bone cancer pain; intrathecal injection of TRL4 siRNA at post-inoculation day 9 could attenuate, but not completely block, well-established bone cancer pain. Conclusions: TLR4 might be the main mediator in the induction of bone cancer pain. Further study of this early, specific, and innate CNS/microglial response, and how it leads to sustained glial/neuronal hypersensitivity, might lead to new therapies for the prevention and treatment of bone cancer pain syndromes.

Monopulse radar is widely used for its high-precision angle measurement and powerful anti-jamming performance. Because the components of radar system are not ideal, the radar measurement accuracy is reduced. According to the structure of sum and difference patterns phase-comparison two-dimension monopulse radar system, the system is divided into three parts, which include the circuit from antenna to sum-difference comparators, the sum-difference comparators and the channel signal processing module. The impacts of their non-ideal to the performance of angle measurement are analyzed and simulated. Some meaningful conclusions are acquired which may bring great convenience to engineering and system design.

We studied the calcium content and mechanical strength of cortical bone from rats and dogs after different periods of demineralisation, showing that the rate of demineralisation differed considerably between the species. Specimens from the rat were further treated by chemical extraction and autolysis and tested for osteoinductive properties. We showed that partially demineralised cortical bone retained adequate mechanical strength, while retaining the biological effects of completely demineralised bone. This shows that it is possible to prepare allografts which have adequate mechanical strength and still retain osteo-inductive properties.

To investigate the internal electromagnetic functional principle, dynamic characteristic and faults operational performance of brushless AC synchronous generator with rotating rectifier in Aeronautic AC power supply, traditional analytical method is restricted by precondition and cannot improve anymore, while finite element method has been widely used for electromagnetic computation. Since few theses adopt finite element method to analysis AC exciter with armature rotating structure of aeronautic AC power supply, this paper takes it for research object. It states the principle and process of two-dimensional transient field simulation modeling with Magnet software. Furthermore, it also simulates field distribution, electromagnetic and circuit parameters under unloading for AC exciter. With contrast to actual values, the model has been proved available to design and optimize this type of machine. Meanwhile, this method can be extended in other aeronautic AC power supply modeling and lays a foundation of optimal design of AC Power Supply system.

Equivalent magnet circuit method is adopted in investigating main generator in three-level synchronous generator system of aeronautic AC power supply. With RMxprt software of Ansoft corporation, it establishes geometrical model and computes primary electrical parameters. Furthermore, with Maxwell 2D software, it attains two-dimensional transient model and simulates magnetic spacial distributing, electromagnetic and circuit parameters under unloading. With contrast to actual measure values, it verifies the correctness of the model. It has been proved available for element encapsulation in further study for other types of aeronautic power supply computational auxiliary design and optimization.

Software package which includes RMxprt for Motor design, Maxwell 2D for electromagnetic computation, Simplorer for complex circuit simulation of Ansoft Corporation has played an role in system simulation fields like a set, but it has disadvantage in design AC exciter in aeronautic AC power supply with armature rotating. There has no input module in RMxprt, therefore this paper establishes two-dimensional transient electromagnetic model for this kind of generator with Maxwell 2D directly and simulates magnetic dimensional distribution, electromagnetic and circuit parameters variation under unloading condition. By contrast with the actual experimental values, it verifies the practicability of the model. Meanwhile, the model can be available to design and optimize this type of machine and other transient investigation analysis.

The motion of current filaments in avalanching PIN diodes has been investigated in this paper by 2D transient numerical simulations. The simulation results show that the filament can move along the length of the PIN diode back and forth when the self-heating effect is considered. The voltage waveform varies periodically due to the motion of the filament. The filament motion is driven by the temperature gradient in the filament due to the negative temperature dependence of the impact ionization rates. Contrary to the traditional understanding that current filamentation is a potential cause of thermal destruction, it is shown in this paper that the thermally-driven motion of current filaments leads to the homogenization of temperature in the diode and is expected to have a positive influence on the failure threshold of the PIN diode.

A two-dimensional electrothermal model of the bipolar transistor (BJT) is established, and the transient behaviors of the BJT originally in the forward-active region are simulated with the injection of electromagnetic pulse from the base. The results show that the damage location of the BJT shifts with the amplitude of the pulse. With a low pulse amplitude, the burnout of the BJT is caused by the avalanche breakdown of the emitter-base junction, and the damage location lies in the cylindrical region of this junction. With a high pulse amplitude, the damage first occurs at the edge of the base closer to the emitter due to the second breakdown of the p-n-n+ structure composed of the base, the epitaxial layer and the substrate. The burnout time increases with pulse amplitude increasing, while the damage energy changes in a decrease-increase-decrease order with it, thus generating both a minimum value and a maximum value of the damage energy. A comparison between simulation results and experimental ones shows that the transistor model presented in the paper can not only predict the damage location in the BJT under intense electromagnetic pulses, but also obtain the damage energy.

This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves (HPMs) through the injection approach. The dependences of the microwave damage power, P, and the absorbed energy, E, required to cause the device failure on the pulse width τ are obtained in the nanosecond region by utilizing the curve fitting method. A comparison of the microwave pulse damage data and the existing dc pulse damage data for the same transistor is carried out. By means of a two-dimensional simulator, ISE-TCAD, the internal damage processes of the device caused by microwave voltage signals and dc pulse voltage signals are analyzed comparatively. The simulation results suggest that the temperature-rising positions of the device induced by the microwaves in the negative and positive half periods are different, while only one hot spot exists under the injection of dc pulses. The results demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy, respectively. The dc pulse damage data may be useful as a lower bound for microwave pulse damage data.

A novel semicircular electrode metal-semiconductor-metal (SEMSM) ultraviolet detector is modeled, investigated and characterized with a self-consistent numerical calculation method. For the purpose of model and performance verification, a comprehensive comparison of the SEMSM detector and a conventional electrode MSM detector is carried out with experimental data. The results indicate that the physical models are able to predict the enhanced device features. Moreover, the structural parameters have been adjusted appropriately to optimize the SEMSM detector. The findings show that a device with a 2 μm finger radius and 3 μm spacing exhibits outstanding characteristics in terms of a peak responsivity of 0.177 A/W at 290 nm, a maximum external quantum efficiency of over 75%, and a comparable normalized photocurrent to dark current ratio of 1.192 × 1011 W−1 at 0.3 V bias. These results demonstrate that the SEMSM detector has excellent performance for optoelectronic integrated circuit applications.

Based on the device operation mechanism and physical model, effects of the improved hetero-material-gate (HMG) approach on deep sub-micron silicon carbide (SiC) metal-semiconductor field-effect transistor (MESFET) are analyzed. By comparing with the conventional MESFET, it is shown that the improved HMG approach induces a multi-stepped distribution of the potential in the channel, leading to an enhanced electric field at the source. Meanwhile, the position of the maximum of the channel potential is changed to the drain side compared with the dual-material-gate (DMG) device, thus the carriers in the channel are accelerated more efficiently and the variation of potential caused by drain voltage is eliminated to a certain degree, resulting in a better restraint in short-channel effect. Also, different technological parameters are designed to study the dependence of the device performance and an optimization plan is obtained, leading to a decreased sub-threshold swing. In addition, asymmetric gate structures are designed for high power application, achieving an improved distribution of the electric field at the gate edge and an enhanced breakdown voltage of the small scale device.