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Post-transplant lymphoproliferative disease (PTLD) is a rare complication accompanying organ transplantation. Herein, we presented 3 cases of PTLD with different primary sites. All three patients presented with symptoms in the corresponding organs or sites and the latter two patients started with atypical symptoms of infections. The first two patients who developed the disease about a year after liver transplantation both had EBV infections. All three patients received immunosuppressant reduction and antiviral therapy. In case 2, remission occurred midway. Adult liver transplantation recipients are at high risk for PTLD, and screening for EBV infection should be intensified in such recipients within 1 year after liver transplantation. Patients should be highly alert for the development of PTLD when new unidentified masses appear, for whom enhanced CT and tissue biopsy should be performed as early as possible. [ABSTRACT FROM AUTHOR]

We introduce a multi-parameter combined objective function of heat engines under the strong coupling and symmetry condition and derive the universal expression of the optimization efficiency. The results obtained show that the optimization efficiency derived from the multi-parameter combined objective function include a variety of optimization efficiencies, such as the efficiency at the maximum power, efficiency at the maximum efficiency-power state, efficiency at the maximum ecological or unified tradeoff function, and Carnot efficiency. It is further explained that these results are also suitable for the endoreversible cycle model of the Carnot heat engines operating between two heat reservoirs. [ABSTRACT FROM AUTHOR]

We theoretically demonstrate that the heat flows can be manipulated by designing a three-terminal quantum-dot system consisting of three Coulomb-coupled quantum dots connected to respective reservoirs. In this structure, the electron transport between the quantum dots is forbidden, but the heat transport is allowed by the Coulomb interaction to transmit heat between the reservoirs with a temperature difference. We show that such a system is capable of performing thermal management operations, such as heat flow swap, thermal switch, and heat path selector. An important thermal rectifier, i.e., a thermal diode, can be implemented separately in two different paths. The asymmetric configuration of a quantum-dot system is a necessary condition for thermal management operations in practical applications. These results should have important implications in providing the design principle for quantum-dot thermal management devices and may open up potential applications for the thermal management of quantum-dot systems at the nanoscale. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAVs) have shown great potential in agriculture and are increasingly being developed for agricultural use. There are still a lot of experiments that need to be done to improve their performance and explore new uses, but experiments using UAVs are limited by many conditions like weather and location and the time it takes to prepare for a flight. To promote UAV remote sensing, a near ground remote sensing platform was developed. This platform consists of three major parts: (1) mechanical structures like a horizontal rail, vertical cylinder, and three axes gimbal; (2) power supply and control parts; (3) onboard application components. This platform covers five degrees of freedom (DOFs): horizontal, vertical, pitch, roll, yaw. A stm32 ARM single chip was used as the controller of the whole platform and another stm32 MCU was used to stabilize the gimbal. The gimbal stabilizer communicates with the main controller via a CAN bus. A multispectral camera was mounted on the gimbal. Software written in C++ language was developed as the graphical user interface. Operating parameters were set via this software and the working status was displayed in this software. To test how well the system works, a laser distance meter was used to measure the slide rail's repeat accuracy. A 3-axis vibration analyzer was used to test the system stability. Test results show that the horizontal repeat accuracy was less than 2 mm; vertical repeat accuracy was less than 1 mm; vibration was less than 2 g and remained at an acceptable level. This system has high accuracy and stability and can therefore be used for various near ground remote sensing studies. [ABSTRACT FROM AUTHOR]

Based on two capacitively coupled quantum dots in the Coulomb-blockade regime, a model of three-terminal quantum-dot refrigerators is proposed. With the help of the master equation, the transport properties of steady-state charge current and energy flow between two quantum dots and thermal reservoirs are revealed. It is expounded that such a structure can be used to construct a refrigerator by controlling the voltage bias and temperature ratio. The thermodynamic performance characteristics of the refrigerator are analyzed, including the cooling power, coefficient of performance (COP), maximum cooling power, and maximum COP. Moreover, the optimal regions of main performance parameters are determined. The influence of dissipative tunnel processes on the optimal performance is discussed in detail. Finally, the performance characteristics of the refrigerators operated in two different cases are compared. [ABSTRACT FROM AUTHOR]

In this paper, we designed the offset frequency locking and active frequency stabilization system for the continuous-wave (CW) and electro-optical Q-switched RF-excited waveguide CO2 lasers to provide an ideal light source for coherent radar. The CW laser is used as a local laser, and the pulsed laser is used as a main laser, which can produce Q-switched and cavity-dumped laser synchronously. A closed-loop laser frequency control system was used to stabilize the Q-switched laser at the gain curve center frequency and to lock the two lasers at a selected heterodyne frequency. The system includes two parts: 1) pulsed laser frequency stabilization and 2) offset frequency locking. The frequency stabilization part can keep the Q-switched laser oscillating at the peak of the gain curve by measuring the pulse build-up time continuously and controlling the cavity length. The offset frequency locking circuits keep the heterodyne frequency around the selected frequency by measuring the frequency of the beat signals and controlling the CW laser cavity length. In the experiment, the long-term frequency shift of the pulse laser was measured to be less than ±16 MHz and the offset frequency fluctuation was less than ±2 MHz when the frequency control system was in a closed-loop operation. [ABSTRACT FROM AUTHOR]

We study the thermodynamic performance of a nanosized photoelectric refrigerator consisting of three coupled single-level quantum dots embedded between two reservoirs at different temperatures. Based on the quantum master equation, we derive expressions for the cooling power and coefficient of performance (COP) of the refrigerator and plot the characteristic curves between the cooling power and the COP. We analyze the optimal performance parameters under conditions of maximum cooling power and maximum COP, and we discuss the influence of the energy level difference and the temperature ratio on the optimal performance parameters in detail. [ABSTRACT FROM AUTHOR]

Providing anonymous communications in mobile ad hoc networks (MANETs) is an effective countermeasure against malicious traffic analysis. This paper presents AOS, an Anonymous Overlay System for MANETs, which provides provably strong source and destination anonymity under a rather strong adversary model. AOS differs significantly from previous anonymous communication systems for MANETs mainly in three aspects. First, AOS is an overlay system independent of the underlying MANET protocol stack. Second, AOS resolves the conflict between anonymous communications and secure routing in MANETs and enables providing both at the same time. Last but not least, AOS can satisfy diverse anonymity requirements with different communication and computation overhead. AOS is the first system of its kind, and its efficacy and efficiency are confirmed by detailed qualitative and quantitative analysis. [ABSTRACT FROM AUTHOR]

Abstract  The proper functioning of mobile ad hoc networks depends on the hypothesis that each individual node is ready to forward packets for others. This common assumption, however, might be undermined by the existence of selfish users who are reluctant to act as packet relays in order to save their own resources. Such non-cooperative behavior would cause the sharp degradation of network throughput. To address this problem, we propose a credit-based Secure Incentive Protocol (SIP) to stimulate cooperation among mobile nodes with individual interests. SIP can be implemented in a fully distributed way and does not require any pre-deployed infrastructure. In addition, SIP is immune to a wide range of attacks and is of low communication overhead by using a Bloom filter. Detailed simulation studies have confirmed the efficacy and efficiency of SIP. [ABSTRACT FROM AUTHOR]

Abstract  Wireless mesh networks (WMNs) are gaining growing interest as a promising technology for ubiquitous high-speed network access. While much effort has been made to address issues at physical, data link, and network layers, little attention has been paid to the security aspect central to the realistic deployment of WMNs. We propose UPASS, the first known secure authentication and billing architecture for large-scale WMNs. UPASS features a novel user-broker-operator trust model built upon the conventional certificate-based cryptography and the emerging ID-based cryptography. Based on the trust model, each user is furnished with a universal pass whereby to realize seamless roaming across WMN domains and get ubiquitous network access. In UPASS, the incontestable billing of mobile users is fulfilled through a lightweight realtime micropayment protocol built on the combination of digital signature and one-way hash-chain techniques. Compared to conventional solutions relying on a home-foreign-domain concept, UPASS eliminates the need for establishing bilateral roaming agreements and having realtime interactions between potentially numerous WMN operators. Our UPASS is shown to be secure and lightweight, and thus can be a practical and effective solution for future large-scale WMNs. [ABSTRACT FROM AUTHOR]

Distributed peer-to-peer (P2P) applications have been gaining momentum recently. In such applications, all participants are equal peers simultaneously functioning as both clients and servers to each other. A fundamental problem is, therefore, how to select reliable servers from a vast candidate pool. To answer this important open question, we present a novel reputation system built upon the multivariate Bayesian inference theory. Our system offers a theoretically sound basis for clients to predict the reliability of candidate servers based on self-experiences and feedbacks from peers. In our system, a fine-grained quality of service (QoS) differentiation method is designed to satisfy the diverse QoS needs of individual nodes. Our reputation system is also application- independent and can simultaneously serve unlimited P2P applications of different type. Moreover, it is semidistributed in the sense that all application-related QoS information is stored across system users either in a random fashion or through a distributed hash table (DHT). In addition, we propose to leverage credits and social awareness as reliable means of seeking honest feedbacks. Furthermore, our reputation system well protects the privacy of users offering feedbacks and is secure against various attacks such as defaming, flattering, and the Sybil attack. We confirm the effectiveness and efficiency of the proposed system by extensive simulation results. [ABSTRACT FROM AUTHOR]

We theoretically propose a simple setup based on a three-terminal triple quantum dot in the Coulomb blockade regime as a heat-flow allocator to spatially separate heat flow along two different channels at arbitrary proportion. We show that a constant output heat-flow ratio can be obtained in a wide range of system parameters, and any ratio of the output heat flow, whether it is an integer ratio or a fractional ratio, can be obtained by directly adjusting the ratio of the energy-dependent tunneling rate. [ABSTRACT FROM AUTHOR]

A new model of the photon-enhanced thermionic emission (PETE) device with a nanoscale vacuum gap is established by introducing the quantum tunnelingeffect and the image force correction. Analytic expressions for both the thermionic emission and tunneling currents are derived. The electron concentration and the temperature of the cathode are determined by the particle conservation and energy balance equations. The effects of the operating voltage on the maximum potential barrier, cathode temperature, electron concentration and equilibrium electron concentration of the conduction band, and efficiency of the PETE device are discussed in detail for different given values of the vacuum gap length. The influence of the band gap of the cathode and flux concentration on the efficiency is further analyzed. The maximum efficiency of the PETE and the corresponding optimum values of the band gap and the operating voltage are determined. The results obtained here show that the efficiency of the PETE device can be significantly improved by employing a nanoscale vacuum gap. [ABSTRACT FROM AUTHOR]

Fujian Key Laboratory of Semiconductor Materials and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, and Department of Physics, Xiamen University, Xiamen 361005, People's Republic of China (Received 17 September 2015; accepted 12 January 2016; published online 27 January 2016) A new model of the photon-enhanced thermionic emission (PETE) device with a nanoscale vacuum gap is established by introducing the quantum tunneling effect and the image force correction. Analytic expressions for both the thermionic emission and tunneling currents are derived. The electron concentration and the temperature of the cathode are determined by the particle conservation and energy balance equations. The effects of the operating voltage on the maximum potential barrier, cathode temperature, electron concentration and equilibrium electron concentration of the conduction band, and efficiency of the PETE device are discussed in detail for different given values of the vacuum gap length. The influence of the band gap of the cathode and flux concentration on the efficiency is further analyzed. The maximum efficiency of the PETE and the corresponding optimum values of the band gap and the operating voltage are determined. The results obtained here show that the efficiency of the PETE device can be significantly improved by employing a nanoscale vacuum gap. [ABSTRACT FROM AUTHOR]

A precise delay system for a streak tube imaging lidar (STIL) is developed. Two delay schemes are designed that are suitable for long- and short-distance lidar imaging. The digital scheme delay can reach 100 µs, and its precision is <6 ns; the analog scheme delay can reach 1200 ns and its precision is <1 ns. Using the STIL system, three-dimensional (3-D) imaging experiments are carried out on land targets at about 2.3-km range and underwater targets at about 25-m range. The experimental results show that the designed delay device can produce precise delay times and effectively verify the 3-D imaging quality of the STIL. This device also has the advantages of stable operation, being more compact, and requiring less power than existing instruments. [ABSTRACT FROM AUTHOR]

We calculate the efficiency at the unified trade-off optimization criterion (the so-called maximum Ω criterion) representing a compromise between the useful energy and the lost energy of heat engines operating between two reservoirs at different temperatures and chemical potentials, and demonstrate that the linear coefficient 3/4 and quadratic coefficient 1/32 of the efficiency at maximum Ω are universal for heat engines under strong coupling and symmetry conditions. It is further proved that the conclusions obtained here also apply to the ecological optimization criterion. [ABSTRACT FROM AUTHOR]

In this paper, a new method of measuring a water-stimulated Brillouin scattering (SBS) frequency shift by optical coherent detection is presented, in order to remote-sense the underwater temperature of the ocean. A single longitudinal mode, passively Q-switched pulsed Nd:YAG laser is used as the light source, the water SBS beam is used as the signal beam, and a portion of the incident laser beam is used as the local oscillator. The heterodyne is detected by a high-speed photodetector, and the heterodyne frequency is the Brillouin frequency shift. Therefore, the underwater temperature can be determined according to the relationship between the Brillouin frequency shift and the water temperature. To test and verify its practicability, the heterodyne waveforms at different water temperatures are recorded in the laboratory with a wide-band oscilloscope, and the Brillouin frequency shifts are deduced by a Fourier transform. The experimental results are consistent with the theoretical analysis. This work provides the foundation for the development of a water temperature measurement system based on coherent Brillouin scattering. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc network (VANET) can offer various services and benefits to users and thus deserves deployment effort. Attacking and misusing such network could cause destructive consequences. It is therefore necessary to integrate security requirements into the design of VANETs and defend VANET systems against misbehavior, in order to ensure correct and smooth operations of the network. In this paper, we propose a security system for VANETs to achieve privacy desired by vehicles and traceability required by law enforcement authorities, in addition to satisfying fundamental security requirements including authentication, nonrepudiation, message integrity, and confidentiality. Moreover, we propose a privacy-preserving defense technique for network authorities to handle misbehavior in VANET access, considering the challenge that privacy provides avenue for misbehavior. The proposed system employs an identity-based cryptosystem where certificates are not needed for authentication. We show the fulfillment and feasibility of our system with respect to the security goals and efficiency. [ABSTRACT FROM AUTHOR]

We propose and investigate the SPREAD scheme as a complementary mechanism to enhance secure data delivery in a mobile ad hoc network. The basic idea is to transform a secret message into multiple shares, and then deliver the shares via multiple paths to the destination so that even if a certain number of message shares are compromised, the secret message as a whole is not compromised. We present the overall system architecture and discuss three major design issues: the mathematical model for the generation and reconstruction of the secret message shares, the optimal allocation of the message shares onto multiple paths in terms of security, and the multipath discovery techniques in a mobile ad hoc network. Our extensive simulation results justify the feasibility and the effectiveness of the SPREAD approach. [ABSTRACT FROM AUTHOR]

A method using rotating Fabry-Perot (FP) mirror to measure CO2 laser wavelength was developed. The variation of FP transmittance changing with laser incident angle was calculated theoretically and the variation curve was given. The calculation illustrates that the variation of FP reflectance with incident angle 0 to 30 deg has little effect on the transmittance of FP. In the experiments, the CO2 laser transmittance variation of FP was measured at a wavelength of 9.27 µm. To improve the measurement precision of the laser wavelength, the method using the centrosymmetric peaks of FP transmittance curve in the range from -20 to +20 deg of laser incident angle was proposed. The precision of the measurement is about 0.01 µm. The experiment result is consistent with theoretical analysis, which demonstrates the feasibility of the laser wavelength measurement using rotating FP method. [ABSTRACT FROM AUTHOR]

This paper presents a kind of miniature handheld laser fluorescence spectrometer, which integrates a laser emission system, a spectroscopic system, and a detection system into a volume of 100 x 50 x 20 mm³. A universal serial bus interface is connected to PC for data processing and spectrum display. The emitted laser wavelength is 405 nm. A spectral range is 400 to 760 nm and 2-nm optical resolution has been achieved. This spectrometer has the advantages of compact structure, small volume, high sensitivity, and low cost. [ABSTRACT FROM AUTHOR]

We present electrically injected GaAs/GaAsBi single quantum well laser diodes (LDs) emitting at a record long wavelength of 1141 nm at room temperature grown by molecular beam epitaxy. The LDs have excellent device performances with internal quantum efficiency of 86%, internal loss of 10 cm-1 and transparency current density of 196 A/cm2. The LDs can operate under continuous-wave mode up to 273 K. The characteristic temperature are extracted to be 125 K in the temperature range of 77~150 K, and reduced to 90Kin the range of 150~273 K. The temperature coefficient of 0.3 nm/K is extracted in the temperature range of 77~273 K. [ABSTRACT FROM AUTHOR]

Objective: To observe the clinical effect of acupuncture at the sphenopalatine ganglion for chronic secretary otitis media (SOM) in children. Methods: A total of 95 children with chronic SOM were randomized into a treatment group of 48 cases and a control group of 47 cases. The treatment group received acupuncture at the sphenopalatine ganglion. The control group was given Myrtol enteric capsules and Mometasone furoate nasal spray. The changes in hearing threshold and middle ear acoustic conductance were observed before treatment and after eight weeks and 12 weeks of treatment to compare the clinical effect between the two groups. Results: The total effective rate was 85.4% in the treatment group and 72.2% in the control group. The difference between the two groups was statistically significant (P < 0.05). Conclusion: Acupuncture at the sphenopalatine ganglion is an effective approach for treating chronic SOM in children. [ABSTRACT FROM AUTHOR]

Effective fault classification of rolling element bearings provides an important basis for ensuring safe operation of rotating machinery. In this paper, a novel vibration sensor-based fault diagnosis method using an Ellipsoid-ARTMAP network (EAM) and a differential evolution (DE) algorithm is proposed. The original features are firstly extracted from vibration signals based on wavelet packet decomposition. Then, a minimum-redundancy maximum-relevancy algorithm is introduced to select the most prominent features so as to decrease feature dimensions. Finally, a DE-based EAM (DE-EAM) classifier is constructed to realize the fault diagnosis. The major characteristic of EAM is that the sample distribution of each category is realized by using a hyper-ellipsoid node and smoothing operation algorithm. Therefore, it can depict the decision boundary of disperse samples accurately and effectively avoid over-fitting phenomena. To optimize EAM network parameters, the DE algorithm is presented and two objectives, including both classification accuracy and nodes number, are simultaneously introduced as the fitness functions. Meanwhile, an exponential criterion is proposed to realize final selection of the optimal parameters. To prove the effectiveness of the proposed method, the vibration signals of four types of rolling element bearings under different loads were collected. Moreover, to improve the robustness of the classifier evaluation, a two-fold cross validation scheme is adopted and the order of feature samples is randomly arranged ten times within each fold. The results show that DE-EAM classifier can recognize the fault categories of the rolling element bearings reliably and accurately. [ABSTRACT FROM AUTHOR]

Effects of the moisture content (MC) of tea on diffuse reflectance spectroscopy were investigated by integrated wavelet transform and multivariate analysis. A total of 738 representative samples, including fresh tea leaves, manufactured tea and partially processed tea were collected for spectral measurement in the 325-1,075 nm range with a field portable spectroradiometer. Then wavelet transform (WT) and multivariate analysis were adopted for quantitative determination of the relationship between MC and spectral data. Three feature extraction methods including WT, principal component analysis (PCA) and kernel principal component analysis (KPCA) were used to explore the internal structure of spectral data. Comparison of those three methods indicated that the variables generated by WT could efficiently discover structural information of spectral data. Calibration involving seeking the relationship between MC and spectral data was executed by using regression analysis, including partial least squares regression, multiple linear regression and least square support vector machine. Results showed that there was a significant correlation between MC and spectral data (r = 0.991, RMSEP = 0.034). Moreover, the effective wavelengths for MC measurement were detected at range of 888-1,007 nm by wavelet transform. The results indicated that the diffuse reflectance spectroscopy of tea is highly correlated with MC. [ABSTRACT FROM AUTHOR]

Recently, multihop wireless mesh networks (WMNs) have attracted increasing attention and deployment as a low-cost approach to provide broadband Internet access at metropolitan scale. Security and privacy issues are of most concern in pushing the success of WMN5 for their wide deployment and for supporting service-oriented applications. Despite the necessity, limited security research has been conducted toward privacy preservation in WMNs. This motivates us to develop PEACE, a novel Privacy-Enhanced yet Accountable security framework, tailored for WMNs. On one hand, PEACE enforces strict user access control to cope with both free riders and malicious users. On the other hand, PEACE offers sophisticated user privacy protection against both adversaries and various other network entities. PEACE is presented as a suite of authentication and key agreement protocols built upon our proposed short group signature variation. Our analysis shows that PEACE is resilient to a number of security and privacy related attacks. Additional techniques were also discussed to further enhance scheme efficiency. [ABSTRACT FROM AUTHOR]

High quality AlAs1−xBix layers with Bi composition of 3%–10.5% have been successfully grown by molecular beam epitaxy. The Bi incorporation is confirmed by Rutherford backscattering spectroscopy. For a 400 nm thick AlAsBi layer, the strain relaxation occurs when the Bi composition is larger than 6.5%. Flux ratio is calculated from Knudsen-cell model and Maxwell equation, according to the geometrical relationship of our equipment. The Bi incorporation increases with increasing the As–Al flux ratio as well as the Bi flux. The extrapolation lattice constant of hypothetic zincblende AlBi alloy is about 6.23 Å. [ABSTRACT FROM AUTHOR]