Ballistic Penetration Damage of Hybrid Thermoplastic Composites Reinforced with Kevlar and UHMWPE Fabrics

Polymer matrix types of fiber hybrid composites are key factors to improve ballistic impact damage tolerances.Here we report ballistic penetration damages of Kevlar/ultra-high molecular weight polyethylene(UHMWPE)hybrid composites with thermoplastic polyurethane(PU)matrix.The hybrid composites were penetrated by fragment-simulating projectiles(FSPs)using an air gun impact system.The effects of stacking sequences on the ballistic performance of hybrid composites were analyzed.Two types of specific energy absorption(the energy absorption per unit area density and the energy absorption per unit thickness)were investigated.It was found that the main damage modes of PU hybrid composites were fiber breakage,matrix damage,fiber pullout and interlayer delamination.The instantaneous deformation could not be used as a reference index for evaluating the ballistic performance of the target plate.The energy absorption process of the PU hybrid composites showed a nonlinear pattern.The hybrid structure affected the specific energy absorption of the materials.

古希腊剧场的起源与发展

古希腊戏剧剧场绝不能看成是单一的公民文化娱乐场所,我们应该站在社会背景和城邦政治文化角度来看待其功能,戏剧演出活动蕴藏着深厚的社会意义,承载着城邦政治文明建设和公民教化的作用。虽然各个时代不同民族的剧场文化存在诸多差异,但剧场自身的职能依旧未变,是传播戏剧文化的物质媒介。露天剧场作为剧场的起源形态,其发展需要政治文化的支持,也离不开艺术文化的积淀。古希腊从迈锡尼文明开始进入“黑暗时代”,建立了全新的政治城邦制度,这一制度推动了古希腊戏剧文明向现代剧场文化转变的进程。

“比象”探源

中国的“比象”思维是一种直接性的思维方式,非常注重以直观的方式来把握天地万物,并且将人事与自然相关联,力图寻求天地万物对人的意义。同时“比象”不脱离具象,就在对自然万物的观照中体认事物背后所蕴含的意义。“比象”思维在汉字的产生、原始艺术、先民四方四时观念等方面体现得尤为明显。这些都是远古先民在直观天地万物的基础上依类象形创造出来的,是“比天”的产物。在原始巫术阶段,天是作为超自然的力量被崇拜的,比天更多地体现为“以天统人”模式下的“比神”。殷周之际,随着人性意识的觉醒,天逐渐祛魅化,演变成为自然之天或者形而上之天,其典型特质被概括为“道”,此时的比天就体现为“以人合天”模式下的“比道”,不再是简单地比天之形,而是对天的运行规律及其形而上特性的认识。因此,比象源于比天,却不限于比天,而是从对天和道的认识出发,由原始巫术的比神发展为礼乐文明的比道,最终发展成为中华民族独特的思维方式。

Lower bound on BER performance for maximal ratio combining with weighting errors

The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.

Ballistic impact simulation of Kevlar-129 fiber reinforced composite material

The penetration resistance of Kevlar-129 fiber reinforced composite materials was investigated with AUTODYN software.The ballistic limits of the fragment that pierced 6kinds of target plates were obtained by finite element simulation when the 10 g fragment simulation projectile（FSP）impacting to the target plates of different thickness values of 8,10,12,14,16 and 18mm with appropriate velocity,respectively,and the influences of thickness on the ballistic limits and the specific energy absorption were analyzed.The results show that the ballistic limit of Kevlar-129 fiber reinforced composite plates presents linear growth with the increase of the target thickness in the range from 8to 18 mm.The specific energy absorption of plates presents approximately linear growth,but there is slightly slow growth in the range from 10 to 16mm of the target thickness.It also can be found that the influences of plate thickness and surface density on the varying pattern of specific energy absorption are almost the same.Therefore,both of them can be used to characterize the variation of specific energy absorption under the impact of the FSP fragment.

文人画的三维视界

"写意"、"比兴"、"体道"是文人画的三维视界。"写意"作为形式层面,从符号学角度确立了文人画的形式特征,它的内涵构成文人画的形式视界;"比兴"作为情感层面,从现象学角度规定了文人画的形象构成,它的内涵构成了文人画的情感视界;"体道"作为意蕴层面,从本体论高度确定了文人画的人文价值,它的内涵构成了文人画的人生视界。

Polymorphisms of alcohol dehydrogenase-2 and aldehyde dehydrogenase-2 and esophageal cancer risk in Southeast Chinese males

AIM： To evaluate the impact of alcohol dehydrogenase-2 （ADH2） and aldehyde dehydrogenase-2 （ALDH2） polymorphisms on esophageal cancer susceptibility in Southeast Chinese males.METHODS： Two hundred and twenty-one esophageal cancer patients and 292 healthy controls from Taixing city in Jiangsu Province were enrolled in this study. ADH2 and ALDH2 genotypes were examined by polymerase chain reaction and denaturing high-performance liquid chromatography. Unconditional logistic regression was used to calculate the odds ratios （OR） and 95% confidence interval （CI）.RESULTS： The ADH G allele carriers were more susceptible to esophageal cancer, but no association was found between ADH2 genotypes and risk of esophageal cancer when disregarding alcohol drinking status. Regardless of ADH2 genotype, ALDH2G/A or A/A carriers had significantly increased risk of developing esophageal cancer, with homozygous individuals showing higher esophageal cancer risk than those who were heterozygous. A significant interaction between ALDH2 and drinking was detected regarding esophageal cancer risk; the OR was 3.05 （95% CI： 2.49-6.25）. Compared with non-drinkers carrying both ALDH2 G/G and ADH2 A/A, drinkers carrying both ALDH2 A allele and ADH2 G allele showed a significantly higher risk of developing esophageal cancer （OR = 8.36, 95% CI： 2.98-23.46）.CONCLUSION： Both ADH2 G allele and ALDH2 A allele significantly increase the risk of esophageal cancer development in Southeast Chinese males. ALDH2 A allele significantly increases the risk of esophageal cancer development especially in alcohol drinkers. Alcohol drinkers carrying both ADH2 G allele and ALDH2 A allele have a higher risk of developing esophageal cancer.

Spatial channel pairing-based maximum ratio combining algorithm for cooperative relay networks

To improve the reliable performance of information transmission in cooperative relay networks, the scheme of the max-rate spatial channel pairing （SCP） based on maximum ratio combining （MRC） is proposed. The scheme includes three steps： channel phase cancellation, MRC, and SCP. Eventually, the solution of the scheme is modeled as convex optimization. The objective function of the optimization problem is to maximize the transmission rate and the optimization variable is the strategy of pairing between the uplink spatial sub-channels of each user and the corresponding downlink spatial ones. The theorem of the arrangement inequalities is adopted to obtain the approximate closed-form solution of the optimal pairing for this convex optimization. Simulation results demonstrate that compared to the existing distributed space-time block coding and coherent combined schemes without SCP, the proposed max-rate SCP plus MRC algorithm achieves appreciable improvements in symbol error rate in medium and high signal-to-noise ratio regimes. The achievable performance gain is due to the use of maxrate SCP.

Highly efficient class-F power amplifier with digital predistortion for WCDMA applications

A digital predistorted class-F power amplifier （PA） using Cree GaN HEMT CGH40010 operating at 2. 12 GHz is presented to obtain high efficiency and excellent linearity for wideband code-division multiple access （ WCDMA ） applications. Measurement results with the continuous wave （CW） signals indicate that the designed class-F PA achieves a peak power-added efficiency （PAE） of 75. 2% with an output power of 39.4 dBm. The adjacent channel power ratio （ACPR） of the designed PA after digital predistortion （DPD） decreases from -28. 3 and -27. 5 dBc to -51.9 and -54. 0 dBc, respectively, for a 4-carrier 20 MHz WCDMA signal with 7. 1 dB peak to average power ratio （PAPR）. The drain efficiency （DE） of the PA is 37. 8% at an average output power of 33. 3 dBm. The designed power amplifier can be aoolied in the WCDMA system.

Controlled Remote Preparation of a Two-Qubit State via an Asymmetric Quantum Channel

I present a new scheme for probabilistic remote preparation of a general two-qubit state from a sender to either of two receivers.The quantum channel is composed of a partial entangled tripartite Greenberger-Horne-Zeilinger (GHZ) state and a W-type state.I try to realize the remote two-qubit preparation by using the usual projective measurement and the method of positive operator-valued measure,respectively.The corresponding success probabilities of the scheme with different methods as well as the total classical communication cost required in this scheme are also calculated.

Generalized Physical Layer Channel Model for RelayBased Super Dense Networks

The κ-μ fading model is an advanced channel model in super dense wireless networks.In this paper,we evaluate the performance of the system over κ-μ fading channel in super dense relay networks with consideration of multiple independent but not necessarily identically distributed(i.n.i.d.) cochannel interference(CCI) under interferencelimited environment.More specifically,we derive a useful and accurate cumulative distribution function(CDF) expression of the end-to-end signal-to-interference plus noise(SINR) ratio.Moreover,we derive novel analytical expressions of the outage probability(OP),average bit error probability(ABEP) and average capacity for binary modulation types and arbitrary positive values of κ-and μ of such system.Furthermore,we propose asymptotic analysis for both the OP and ABEP to give physical insights.A simplified analytical form for the ABEP at high-SNR regimes is provided as well.Finally,the accuracy of the derived expressions is well validated by Monte Carlo simulations.

Compressed SNR-and-Channel Estimation for Beam Tracking in 60-GHz WLAN

Signal-to-noise ratio （SNR） and channel estimations are critical for 60-GHz communications to track the optimal trans- mission and reception beam pairs. However, the excessive pilot overhead for the estima- tions severely reduces system throughput in fast-rotation scenarios. In order to address this problem, we firstly demonstrate the potential sparseness property of 60-GHz channel in beam tracking; subsequently, via exploiting this property, we propose a novel compressed SNR-and-channel estimation. The estimation is conducted in a three-stage fashion, includ- ing the unstructured estimation, nonzero-tap detection, and structured estimation with non- zero-tap location. Numerical simulations show that, in the case of substantial reduction of the pilot overhead, the proposed estimator still reveals a significant improvement in terms of estimation performance over the scheme in IEEE 802.1 lad. Furthermore, it is also demon- strated that the proposed SNR and channel estimators can approach the lower bounds in sparse channels so long as SNR exceeds 8 dB.

Schemes for Splitting Quantum Information with Four-Particle Genuine Entangled States

We propose two schemes for splitting single- and two-qubit states by using four-particle genuine entangled state as the quantum channel. After the sender performs Bell-basis （or three-partite GHZ- basis） measurements on her particles, and the cooperators operate single-particle measurements on their particles, the state receiver can reconstruct the original state of the sender by applying the appropriate unitary operation. In particular, in the scheme for splitting two-qubit state, the receiver needs to introduce an auxiliary particle and carries out a C-NOT operation.

Study and application on fire extinguishing and preventing with light-paste material for coalmine

For preventing and extinguishing the spontaneous combustion of coal seam, based on the importance for sealing air leakage channels in roadway, developed a material of light-paste for coalmine, and research its ingredient, proportion and performance. The result indicates that the component ratio of the material is which PB exciting agent is 20%, complex reinforcing agent is 2%, complex expansion agent is 1%, and A-material is 77%. The performances of compressive strength, swelling ratio and expansion time are optimum. The light-paste material can effectively seal air leakage channels for preventing and extinguishing the spontaneous combustion of coal seam in coalmine.

HIGH SNR SUM CAPACITY ANALYSIS OF BD MIMO BC SYSTEMS WITH IMPERFECT CSI

We investigate the sum capacity of Block Diagonalization precoding Multiple Input Mul-tiple Output Broadcast Channels(BD MIMO BC) with imperfect Channel State Information(CSI) at the base station.Since it is difficult to obtain the exact expression,a lower and an upper bounds of the sum capacity under Gaussian channel estimation errors are drived instead.Analyses show that the gap between two bounds is considerably tight at all Signal to Noise Ratio(SNR) region.From the lower bound of the sum capacity,we can see that the multiplexing gain tends to be zero at high SNR region,which indicates that the BD MIMO BC system with channel estimation errors is interference-limited at high SNR.

New Precoded Spatial-Multiplexing for an Erasure Event in Single Frequency Networks

In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the average bit error rate(BER) is evaluated and minimized through a mathematical analysis. Compared to an ordinary SM, the proposed scheme guarantees identical BER performance under non-erasure fading channels and achieves a greatly improved performance under erasure fading channels, especially for a higher erasure-ratio and SNR values. This improvement is mainly due to the increase in the diversity gain incurred by the optimized precoder over the erasure event. We also compare the performance of the proposed SM to that of the conventional constellation-rotation(CR) scheme applied to the single antenna SFN systems. The results of a computer simulation show that the performance of the new scheme is more effective than that of a conventional CR across all simulation cases.

IMPROVED FXLMS ALGORITHM BASED ON ADAPTIVE NOTCH FILTER APPROACH

An improved algorithm is presented to identify the secondary path based on the adaptive notch filter approach. Since the interference from the narrow band excitation signal is suppressed by the adaptive notch filter, the convergent speed of the on-line control path identification process is significantly improved. As a result, the controller performance is greatly enhanced. Besides the algorithm development, some important factors, such as the influence of reference signal on the controller convergent speed, are also discussed. The effectiveness of the algorithm is verified by experimental results.

Experiments on Channel Evolution Caused by Check-dam Failure

A 10 m long,0.2 m wide flume was employed to simulate the channel bed evolution of check-dam failure.The experiment longitudinal profiles,the gradient of channel bed,head-cutting propagation distance and deposition length were compared with the theoretical solution derived from a sediment transport diffusion equation.In contrast with the theoretical solution,two different gradients were obtained upstream and downstream of the check-dam.The theoretical solution provides a good description of the changes upstream of the check-dam. The ratio of clear water depth to sediment moving layer thickness in the experiment was analyzed and showed that high concentration sediment laden flow was taken in the incipient of check-dam failure,which may be the reason why the experiment result was slightly different from the theoretical solution in the downstream of check-dam.

MAKING FULL USE OF OUTDATED CHANNEL ESTIMATES FOR BLOCK BY BLOCK ADAPTIVE MODULATIONS

This paper explores the potential to use accurate but outdated channel estimates for adaptive modulation. The work is novel in that the research is conditioned on block by block adaptation. First,we define a new quantity,the Tolerable Average Use Delay (TAUD),which can indicate the ability of an adaptation scheme to tolerate the delay of channel estimation results. We find that for the variable-power schemes,TAUD is a constant and dependent on the target Bit Error Rate (BER),average power and Doppler frequency; while for the constant-power schemes,it depends on the ad-aptation block length as well. At last,we investigate the relation between the delay tolerating per-formance and the spectral efficiency and give the system design criterion. The delay tolerating per-formance is improved at the price of lower data rate.

Three-Party Quantum State Sharing of an Arbitrary Unknown Two-Qubit State Based on Entanglement Swapping and Bell-State Measurements

We propose a scheme for sharing an arbitrary unknown two-qubit state among three parties by using afour-qubit cluster-class state and a Bell state as a quantum channel With a quantum controlled phase gate (QCPG)operation and a local unitary operation,any one of the two agents has the access to reconstruct the original state ifhe/she collaborates with the other one,whilst individual agent obtains no information.As all quantum resource canbe used to carry the useful information,the intrinsic efficiency of qubits approaches the maximal value.Moreover,thepresent scheme is more feasible with present-day technique.