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Go provides a new concurrency mechanism based on message-passing, which brings a series of new concurrency bugs. The existing tools are highly dependent on model-checking methods in which they take the source program as the input of model-checking tools to detect the potential concurrent bugs. However, these methods can only qualitatively obtain the concurrency of the program but not obtain the exact number of concurrency bugs in the program. Meanwhile, these approaches are not sensitive to dead codes, which are prone to false negatives. Furthermore, few works have been done on detecting WaitGroup-related bugs in Go concurrent programming, which may cause deadlock. To this end, this paper proposes a novel approach GoDetector to detect concurrent bugs. GoDetector uses a detecting algorithm and a pushdown automaton to verify the channel-related concurrent bugs and WaitGroup-related concurrent bugs separately. To support the evaluation of the tool, 30 benchmarks are collected from the existing tools. GoDetector reports 2 channel safety errors, 29 deadlocks, and 11 WaitGroup-related errors. Compared with the existing tool Godel, GoDetector has the capacity to report more concurrency bugs and fewer false positives. GoDetector also offers additional support for the detection of WaitGroup variables. The experimental results indicate that GoDetector is more efficient at detecting the concurrency in regards to accuracy and diversity.

The lithium niobate (LiNbO3) metasurface is an attractive platform for nonlinear frequency conversion due to its excellent nonlinearity, high damage threshold, and strong enhancement of the driving field. Here, we demonstrated the nonlinear metasurface for terahertz (THz) generation from LiNbO3 on an insulator. The THz electric field from the LiNbO3 metasurface of 300 nm thickness is enhanced by more than one order of magnitude compared to the unstructured sample. The enhanced terahertz electric field is very selective in the excitation wavelength due to its resonant feature and is highly anisotropic with respect to the excitation polarization. The polarization direction of the THz electric field can be controlled by rotating the optical axis of the LiNbO3 metasurface. By combining the nanofabrication technology of the LiNbO3 metasurface and ultrafast nonlinear optics, our work paves the way for the design of new compact terahertz photonic devices that integrate THz emitters into LiNbO3-based chips with multifaceted capabilities.

To improve the correctness of data race detection, an approach to the data race detection based on the context-sensitive analysis in multithreaded programs was proposed. Firstly, control flow analysis was used to construct context-sensitive call graphs, and then escape analysis was employed to find thread-escaped objects that may cause data race. Secondly, context-sensitive alias analysis was conducted to reduce false positives and false negatives. Finally, the happens-before analysis was performed to remove false positives caused by ignoring thread interactions. A data race detection tool ConRacer was implemented in WALA framework based on this approach and was compared with the existing tools SRD and RVPredict. The experimental results show that ConRacer is the most precise tool compared with SRD and RVPredict and it can not only detect data races, but also reduce false positives and false negatives effectively. ConRacer improves the detection accuracy by combining context-sensitive with static detection methods, which has certain reference value for discovering concurrent errors and optimizing software performance.

With the rapid development of urbanization and industrialization, the problem of air pollution has become increas-ingly prominent, and air quality prediction is particularly important. Some representative studies currently monitor and forecast air quality in real time. For example, ZHOU Guangqiang et al. Used numerical prediction to analyze air quality in eastern China. However, experimental results show that this method is difficult to predict and is very important. SANKAR et al. Used multiple linear regression to predict air quality, but the experimental results showed that the linear model had low prediction accuracy and slow efficiency;PREZ et al. Used statistical methods to predict air quality, and the experimental results proved the prediction accuracy of the statistical method relatively low; WANG et al. Used an improved BP neural network to establish a prediction model for the air quality index, and their experiments verified that the BP neural network has a slow convergence rate and is prone to fall into the local optimal solution problem; YANG et al. Air quality concentration effect, a PM2.5 concentration prediction model based on random forests was established, and the empirical process proved that the meshing program weakened the quality and efficiency of subsequent air quality analysis; these methods are difficult to model from a time perspective, and the prediction accuracy is low is a more important issue. Because low prediction accuracy may lead to large errors in air quality prediction results. 河北科技大学学报 2020年 第1期 张冬雯，等:基于长短期记忆神经网络模型的空气质量预测 In this paper, a neural network model based on long -term memory (LSTM) is proposed to solve the problem of low prediction accuracy in air quality research.MAPE, RMSE, R, IA and MAE were used to test the predictive performance of LSTM neural network and the comparison model.Since Delhi and Houston are cities with high levels of air pollution, the experimental data sets used in this paper were from the air quality data of Punjabi Bagh monitoring station in Delhi from 2014 to 2016 and the air quality data of Harris County monitoring station in Houston from 2010 to 2016.By comparing LSTM neural network with multiple linear regression and regression model (SVR), the experimental results show that LSTM neural network is suitable for time series prediction with multiple variables or multiple inputs LSTM neural network has the advantages of high prediction accuracy, high speed and strong robustness.

To improve the recognition model accuracy of crop disease leaves and locating diseased leaves, this paper proposes an improved Faster RCNN to detect healthy tomato leaves and four diseases: powdery mildew, blight, leaf mold fungus and ToMV. First, we use a depth residual network to replace VGG16 for image feature extraction so we can obtain deeper disease features. Second, the k-means clustering algorithm is used to cluster the bounding boxes. We improve the anchoring according to the clustering results. The improved anchor frame tends toward the real bounding box of the dataset. Finally, we carry out a k-means experiment with three kinds of different feature extraction networks. The experimental results show that the improved method for crop leaf disease detection had 2.71% higher recognition accuracy and a faster detection speed than the original Faster RCNN.

Traffic dynamics on multi-layer networks are of great importance to alleviate traffic congestion of real networks. In this work, we focus on information transport in multi-layer networks comprised of two coupled subnetworks. We investigate the relationship between correlated inter-layer couplings and resource allocation strategies on the traffic dynamics of multi-layer networks. Simulation results show that assortative coupling (AC) structure can improve the multi-layer networks traffic capacity more better than disassortative coupling (DC) and random coupling (RC) with degree-based (DE) efficient resources allocation strategy, and DC structure is better in enhancing the traffic capacity with the simplest average resources allocation (SA) strategy. Our work may shed some light on the traffic dynamics on multi-layer networks.

Two entirely different Cauchy functional equations have been investigated in the literature with a couple of unknown operators f and g mapping a unitary ring X into a domain of integrity Y satisfying the elimination law and keeping the operations of addition about operator f and multiplication about operator g, respectively. A total of four studying syzygies achieved by multiplying these two fundamental Cauchy functional equations side by side are investigated. The novelty of the literature is to find out sufficient conditions upon [Formula: see text] deriving the model to be produced a strongly alienation phenomenon by using some new computation techniques.

Abstract Ferroelectric materials have been a key research topic owing to their wide variety of modern electronic and photonic applications. For the quick exploration of higher operating speed, smaller size, and superior efficiencies of novel ferroelectric devices, the ultrafast dynamics of ferroelectrics that directly reflect their respond time and lifetimes have drawn considerable attention. Driven by time‐resolved pump‐probe spectroscopy that allows for probing, controlling, and modulating dynamic processes of ferroelectrics in real‐time, much research efforts have been made to understand and exploit the ultrafast dynamics of ferroelectric. Herein, the current state of ultrafast dynamic features of ferroelectrics tracked by time‐resolved pump‐probe spectroscopy is reviewed, which includes ferroelectrics order parameters of polarization, lattice, spin, electronic excitation, and their coupling. Several potential perspectives and possible further applications combining ultrafast pump‐probe spectroscopy and ferroelectrics are also presented. This review offers a clear guidance of ultrafast dynamics of ferroelectric orders, which may promote the rapid development of next‐generation devices.

More than ten years after Justyna Sikorska [8] attempted to solve the Heyers-Ulam stability of a single variable equation by using direct method. In this paper, we will improve the results of Justyna Sikorska by using a more efficient approach. Relations between the generalized functional equation, the dependence of their different parameters and several properties are also further explored. To achieve the problem, we try to develop some new techniques to overcome the fundamental difficulties caused by the different properties of the function and the presence of several variables in the equation. Furthermore, we continue to construct and study a couple of functional equations by making a new direct method.

Developers of parallel programming are faced with choices of using various Java locks. Choosing the best lock is a challenging task because a multithreaded application implemented using different locks may end up with uncertain performance. There is a strong need for automated tool support that helps Java programmers choose the best lock for each specific application. This paper presents an automated transformation approach to convert an implementation using a synchronized lock to a ReentrantLock or a ReentrantReadWriteLock at the bytecode level. For the ReentrantLock, our approach runs analysis for global monitors using the visitor pattern in the Joeq compiler. For the ReentrantReadWriteLock, a read or write lock is chosen after a side-effect analysis. Then, the proposed system validates the consistency of the analysis results to ensure a correct sequence of lock usage. Finally, lock operations and related thread communication operations are transformed into a ReentrantLock or a ReentrantReadWriteLock using a bytecode transformation framework Javassist. We validate our approach on several benchmarks including RBTree, PC, SPECjbb2005, and HSQLDB. The experimental results show that the proposed automated transformation approach can transform these benchmarks successfully in a timely fashion.

StampedLock, proposed in JDK 1.8, provides many interesting features, such as optimistic read locks and upgrading/downgrading locks to improve the design of concurrent programs instead of employing pure read/write locks. Existing refactorings have proposed algorithms to convert locks, but there are a few refactorings that use these promising features of StampedLock. To illustrate a possible refactoring, this paper first shows three code transformations based on StampedLock. Then, this paper presents CLOCK, an automated refactoring tool that helps developers convert the synchronized lock into the StampedLock. An algorithm for reentrance analysis is proposed for the precondition validation. The write lock, read lock, optimistic read lock, and upgrading/downgrading lock are inferred and refactored. CLOCK is evaluated with the SPECjbb2005 benchmark and two real-world applications, Xalan and FOP. A total of 66 classes are modified by searching approximately 395KSLOC and applying the refactoring, achieving an average of 22 classes per benchmark. The experimental results show that CLOCK can help developers with refactoring for StampedLock and save developer effort.

Understanding the evolution of molecular electronic structures is the key to explore and control photochemical reactions and photobiological processes. Subjected to strong laser fields, electronic holes are formed upon ionization and evolve in the attosecond timescale. It is crucial to probe the electronic dynamics in real time with attosecond-temporal and atomic-spatial precision. Here, we present molecular attosecond interferometry that enables the in situ manipulation of holes in carbon dioxide molecules via the interferometry of the phase-locked electrons (propagating in opposite directions) of a laser-triggered rotational wave packet. The joint measurement on high-harmonic and terahertz spectroscopy (HATS) provides a unique tool for understanding electron dynamics from picoseconds to attoseconds. The optimum phases of two-color pulses for controlling the electron wave packet are precisely determined owing to the robust reference provided with the terahertz pulse generation. It is noteworthy that the contribution of HOMO-1 and HOMO-2 increases reflecting the deformation of the hole as the harmonic order increases. Our method can be applied to study hole dynamics of complex molecules and electron correlations during the strong-field process. The threefold control through molecular alignment, laser polarization, and the two-color pulse phase delay allows the precise manipulation of the transient hole paving the way for new advances in attochemistry.

We investigate the Hyers–Ulam stability of an equation involving a single variable of the form ∥f(x)−αf(kn(x))−βf(kn+1(x))∥⩽u(x) where f is an unknown operator from a nonempty set X into a Banach space Y, and it preserves the addition operation, besides other certain conditions. The theory is employed and stability theorems are proven for various functional equations involving several variables. By comparing this method with the available techniques, it was noticed that this method does not require any restriction on the parity, on the domain, and on the range of the function. Our findings suggest that it is very much easy and more appropriate to apply the proposed method while investigating the stability of functional equations, in particular for several variables.

The software architecture of Internet of Things defines the component model and interconnection topology of Internet of Things systems. Refactoring is a systematic practice of improving a software structure without altering its external behaviors. When the Internet of Things software is refactored, it is necessary to detect the correctness of Internet of Things software to ensure its security. To this end, this article proposes a novel refactoring correction detection approach to ensure software security. Control flow analysis and data flow analysis are used to detect code changes before and after refactoring, and synchronization dependency analysis is used to detect changes in synchronization dependency. Three detection algorithms are designed to detect refactoring correctness. Four real-world benchmark applications are used to evaluate our approach. The experimental results show that our proposed approach can ensure correctness of Internet of Things software refactoring.

During the OPA (optical parametric amplifier) processes pumped by a high-energy laser, the phase distortion of pump light will transmit to the signal light inevitably. As a result, the beam quality of amplified signal will become poor. In this article, a hybrid seeding scheme with a paired two-stage OPA system is used, where the first and second stages used the signal and the idler as seed sources, respectively. The numerical results show that the hybrid seeding OPA scheme can suppress the phase distortion transformation from pump to signal in both spatial and temporal domains. Consequently, the phase of output signal is well restored to its input state. Because of the restriction removal of beam quality for pump light under the conventional birefringent phase-matching method, this scheme had a good application prospect in high-energy OPA or optical parametric chirped pulse amplification systems.

CoDA (Communities through Directed Affiliations) algorithm is a kind of community detection algorithm which can successfully detect 2-mode communities based on probability model. The F-measure criterion, for information retrieval, is adapted to the evaluation of CoDA algorithm in directed networks with overlapping communities or non-overlapping communities. The value of F1-measure in F-measure criterion can reflect whether CoDA algorithm performs well or not. The data sets used in the experiment is generated by the LFR Benchmark tool. The minimum number of nodes in data set is 100 and the maximum is 20 000, and evaluated experiment is conducted when every 100 nodes is added. The results show that CoDA algorithm performs well when the number of nodes is bellow 1 600. CoDA algorithm's performance becomes worse with the increase of the number of nodes, which proves the CoDA algorithm based on probability model is applicable to the community detection of small-scale networks.

In the optical parametric amplifier (OPA) process, the phase of the pump is transmitted to the amplified signal due to the spatial walk-off effect and/or a temporal group velocity mismatch (GVM) effect between coherent light waves. As a result, the quality of amplified signal will be reduced by the phase distortion and variation of beam equality of the pump pulse. By using a pair of OPAs, the signal and idler are chosen as seeding lights in the front and back stages, respectively, so that the phase of the amplified signal can be restored, and the influence of phase distortion and beam equality deterioration of pump pulse can be eliminated. The present article also reports other characteristics of this hybrid seeded scheme, including accepted bandwidth, spectral purity, and conversion efficiency.

Aiming at a class of discrete-time stochastic systems with Markov jump features, the state-feedback predictive control problem under probabilistic constraints of input variables is researched. On the basis of the concept and method of the multi-layer probabilistic sets, the predictive controller design algorithm with the soft constraints of different probabilities is presented. Under the control of the multi-step feedback laws, the system state moves to different ellipses with specified probabilities. The stability of the system is guaranteed, the feasible region of the control problem is enlarged, and the system performance is improved. Finally, a simulation example is given to prove the effectiveness of the proposed method.

Specific to the selective forwarding attack on routing in cognitive radio network, this paper proposes a trust-based secure routing model. Through monitoring nodes' forwarding behaviors, trusts of nodes are constructed to identify malicious nodes. In consideration of that routing selection-based model must be closely collaborative with spectrum allocation, a route request piggybacking available spectrum opportunities is sent to non-malicious nodes. In the routing decision phase, nodes' trusts are used to construct available path trusts and delay measurement is combined for making routing decisions. At the same time, according to the trust classification, different responses are made specific to their service requests. By adopting stricter punishment on malicious behaviors from non-trusted nodes, the cooperation of nodes in routing can be stimulated. Simulation results and analysis indicate that this model has good performance in network throughput and end-to-end delay under the selective forwarding attack.

To achieve the commercialization of lithium-sulfur (Li-S) batteries, there is a big challenge to improve the sulfur content and sulfur loading of sulfur cathodes. Although carbonaceous materials can improve the sulfur content and sulfur loading, the addition of binders and conductive agents limits the increase in energy density to a great extent. Here, carbon-free titanium nitride nanobelt (TiN-NB) thin films with flexible, conductive, hierarchically porous, and free-standing structures have been successfully developed to construct high-sulfur-loading and high-energy-density sulfur electrodes. In addition, macroscopically intertwined 3D nanobelt networks can provide an effective transport path for lithium ions and electrons, and a microscopically high specific surface area and porosity provide a necessary guarantee for the adsorption and catalytic transformation of polysulfides. At a sulfur loading of 1.0 mg cm-2, the TiN-900@S electrode delivers an initial capacity of 1436.7 mAh g-1. After 150 cycles, the reversible capacity still remains at 1032.6 mAh g-1 at 0.5C. Precisely, at a high sulfur loading of 7.1 mg cm-2, the discharge capacity of the TiN-900@S electrode is maintained at 403.1 mAh g-1 after 50 cycles at 0.1C. [ABSTRACT FROM AUTHOR]

Data race probably occurs when many threads concurrently access the same memory location and at least one is a write thread. Data race detection suffers from false negatives and false positives. How to detect data race and avoid false negatives and false positives has become a hot topic. This paper proposes a static data race detection methodology to eliminate false negatives and false positives. We use Soot to conduct intra-thread and inter-thread analysis. Our data race detection focuses on variable access events that are collected from call graphs. Several program analysis technologies, such as alias variable analysis, alias lock analysis, happens-before analysis, constraint graph, and slicing analysis, are used to improve the coverage and precision of the detection results. In the experimentation, several benchmarks, such as raytracer, sor, and mergesort, have been selected to evaluate our methodology. Experimental results show that SRD can not only eliminate fake races but also identify potential races. Furthermore, SRD can detect more positive races than the existing tool RVPredict. [ABSTRACT FROM AUTHOR]

The objective of the present study was to evaluate the application of dual-source CT perfusion imaging and MRI for the diagnosis of primary liver cancer. Sixty-three patients with primary liver cancer were selected between February 2015 and May 2016. All patients underwent examinations by dual-source CT perfusion imaging and MRI. The perfusion parameters of the focus center and normal liver parenchyma by CT examination and the hemodynamic parameters of the focus center and normal liver parenchyma by MRI examination were analyzed. The accuracy rates of the three detection methods (CT perfusion imaging, MRI, and combined examination) were analyzed and compared by ROC curves. Dual-source CT perfusion imaging revealed that blood flow and blood volume of the focus center were significantly higher than those of normal liver parenchyma (P<0.05). MRI examination showed that hepatic arterial perfusion and hepatic perfusion index of the focus center were significantly higher than those of normal liver parenchyma; portal venous perfusion of the focus center was significantly lower than that of normal liver parenchyma (P<0.05); the difference in total liver perfusion between the focus center and normal liver parenchyma was not significant (P>0.05); the accuracy rates of CT perfusion imaging, MRI, and combined examination were 76.19, 85.71, and 95.24% respectively; the area under the curve of CT perfusion imaging was 0.753 (P<0.05), the sensitivity was 79.2% and the specificity was 74.7%; the area under the curve of MRI was 0.846 (P<0.05), the sensitivity was 84.6%, and the specificity was 80.5%; the area under the curve of CT combined with MRI was 0.947 (P<0.05), the sensitivity was 94.6%, and the specificity was 86.5%. In conclusion, the effect of dual-source CT perfusion imaging combined with MRI for examination of primary liver cancer is superior to that of single use of CT or MRI, and has high clinical application and popularization value. [ABSTRACT FROM AUTHOR]

In this work, we characterize the transmission properties of the focusing-laser-induced filament by using terahertz (THz) time domain spectroscopy. Significant resonance absorption of the THz wave is identified, which is attributed to the dynamic screening of the ionized electrons. The polarization and intensity of the filament-generated pulse have been varied to study their influences on the resonance absorption. Our results suggest that the electron density of the filament can be determined by fitting the phase shifts and absorption properties around the absorption. This method provides not only an alternative to the plasma diagnostics with plasma frequency at the THz range, but also a supplement to the existing generation theory of THz waves from plasma. [ABSTRACT FROM AUTHOR]

Terahertz radiation from tunneling ionization of gaseous atoms and molecules in the two-color laser fields with various polarizations has been investigated. We experimentally demonstrate that the efficiency of terahertz emission in the circularly polarized laser fields with the same helicity is 5 times higher than that with linearly polarized two-color femtosecond pulses in high laser intensity. By solving time-dependent Schrödinger equation, this enhancement is well explained based on the analysis of electron tunneling ionization and subsequent dynamics. [ABSTRACT FROM AUTHOR]

Electro-optic effects of PbZr0.52Ti0.48O3 (PZT) and BaTiO3 (BTO) ferroelectric thin films in the terahertz frequency range are studied with high-sensitive terahertz time-domain spectroscopy. A linear response of PZT film with the linear electro-optic coefficient rc  = 6.73 × 10−11 m/V and a quadratic response of BTO film with the second-order electro-optic coefficient Rc  = 1.42 × 10−17 m2/V2 are observed at the frequency of 1 terahertz under the applied static electric field less than 80 kV/cm. The calculation of rc and Rc based on the Landau-Devonshire free energy theory explains the different electro-optic effects of PZT and BTO well. [ABSTRACT FROM AUTHOR]

Background In a deforming anatomic environment, the motion of an instrument suffers from complex geometrical and dynamic constraints, robot assisted minimally invasive surgery therefore requires more sophisticated skills for surgeons. This paper proposes a novel dynamic virtual fixture (DVF) to enhance the surgical operation accuracy of admittance-type medical robotics in the deforming environment. Methods A framework for DVF on the Euclidean Group SE(3) is presented, which unites rotation and translation in a compact form. First, we constructed the holonomic/ non-holonomic constraints, and then searched for the corresponded reference to make a distinction between preferred and non-preferred directions. Second, different control strategies are employed to deal with the tasks along the distinguished directions. The desired spatial compliance matrix is synthesized from an allowable motion screw set to filter out the task unrelated components from manual input, the operator has complete control over the preferred directions; while the relative motion between the surgical instrument and the anatomy structures is actively tracked and cancelled, the deviation relative to the reference is compensated jointly by the operator and DVF controllers. The operator, haptic device, admittance-type proxy and virtual deforming environment are involved in a hardware-in-the-loop experiment, human-robot cooperation with the assistance of DVF controller is carried out on a deforming sphere to simulate beating heart surgery, performance of the proposed DVF on admittance-type proxy is evaluated, and both human factors and control parameters are analyzed. Results The DVF can improve the dynamic properties of human-robot cooperation in a low-frequency (0 ~ 40 rad/sec) deforming environment, and maintain synergy of orientation and translation during the operation. Statistical analysis reveals that the operator has intuitive control over the preferred directions, human and the DVF controller jointly control the motion along the non-preferred directions, the target deformation is tracked activly. Conclusions The proposed DVF for an admittance-type manipulator is capable of assisting the operator to deal with skilled operations in a deforming environment. [ABSTRACT FROM AUTHOR]

Argon atom ionizing in the ultrafast two-colour field has been used to investigate the physical mechanism of terahertz (THz) generation. We measured simultaneously pulse energies of THz and high-harmonics as the phase delay between the fundamental and its second harmonic was varied. The optimal phase delay of THz generation is determined according to the inherent attochirp of the emitted high-harmonics. The dynamic analysis of the tunnelling electron wave packet driven by the Coulomb-laser coupling shows that laser-assisted soft collisions of the electron wave packet with the atomic core play a key role. it is demonstrated that the rescattering process, being indispensable in high-harmonic generation processes, dominates THz wave generation as well in a more elaborate way. [ABSTRACT FROM AUTHOR]

Background: Robot-assisted needle steering facilitates the percutaneous renal access (PRA) for their accuracy and consistency over manual operation. However, inaccurate image-robot correspondence and uncertainties in robot parameters make the needle track deviate from the intrarenal target. This paper aims to simplify the image-tracker -robot registration procedure and improves the accuracy of needle alignment for robot assisted ultrasound-guided PRA. Methods: First, a semi-automatic rigid registration is used for the alignment of the preoperative MR volume and the intraoperative orthogonal US slices. Passive markers are mounted both on US probe and robot end-effector, the planned puncture path is transferred from the MR volume frame into optical tracker frame. Tracker-robot correspondence and robot calibration are performed iteratively using a simplified scheme, both position and orientation information are incorporated to estimate the transformation matrix, only several key structural robot parameters and joint zeropositions are calibrated for simplicity in solving the inverse kinematic. Furthermore, an optical tracker feedback control is designed for compensating inaccuracies in robot parameters and tracker-robot correspondence, and improving the accuracy of needle alignment. The intervention procedure was implemented by a telemanipulated 5R1P robot, two experiments were conducted to validate the efficiency of robot-tracker registration method and the optical tracker feedback control, robot assisted needle insertion experiment was conducted on kidney phantom to evaluate the system performance. Results: The relative positioning accuracy of needle alignment is 0.24±0.08 mm, the directional accuracy is 6.78±1.65 × 10-4rad; the needle-target distance of needle insertion is 2.15±0. 17 mm. The optical tracker feedback control method performs stable against wide range of angular disturbance over (0 ∼ 0.4) radians, and the length disturbance over (0 ∼ 100) mm. Conclusions: The proposed optical tracker based robot registration and servoing method is capable of accurate three dimension needle operation for PRA procedure with improved precision and shortened time. [ABSTRACT FROM AUTHOR]

We perform a joint measurement of terahertz waves and high-harmonics generated from argon atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase delay between the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in high-harmonic generation processes, dominates THz wave generation as well in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics. [ABSTRACT FROM AUTHOR]

Isolated attosecond pulses with a duration of 88 as are generated in the spectral range of 29–72 eV using double optical gating technique. The gate width is set to be shorter than half the optical cycle to avoid carrier envelop phase stabilization of the 4.2 fs driving laser pulses centered at 800 nm. The attosecond pulse duration is measured with the technique of frequency resolved optical gating for complete reconstruction of attosecond bursts. [ABSTRACT FROM AUTHOR]

We present the experimental and theoretical details of our recent published letter Huang et al (2015 Phys. Rev. Lett.115 123002) on synchronized high-harmonic and terahertz-wave spectroscopy (HATS) from nonadiabatically aligned nitrogen molecules in dual-color laser fields. By associating alignment-angle dependent terahertz wave generation (TWG) with high harmonic generation (HHG), the angular differential photoionization cross section (PICS) for molecules can be reconstructed. The angles at which the PICS’s minima are located show great convergence between the theoretical predictions and the experimentally deduced results when choosing a suitable internuclear distance. We also show the optimal relative phase between the dual-color laser fields for TWG does not change with the alignment angle at a precision of about 50 attoseconds. This all-optical method provides an alternative for investigating molecular structures and dynamics. [ABSTRACT FROM AUTHOR]

We report the synchronized measurements of terahertz wave generation and high-harmonic generation from aligned nitrogen molecules in dual-color laser fields. Both yields are found to be alignment dependent, showing the importance of molecular structures in the generation processes. By calibrating the angular ionization rates with the terahertz yields, we present a new way of retrieving the angular differential photoionization cross section (PICS) from the harmonic signals which avoids specific model calculations or separate measurements of the alignment-dependent ionization rates. The measured PICS is found to be consistent with theoretical predications, although some discrepancies exist. This all-optical method provides a new alternative for investigating molecular structures. [ABSTRACT FROM AUTHOR]