Comparative Study of the Reliability and Complexity of Symmetrical and Asymmetrical Cryptosystems for the Protection of Academic Data in the Democratic Republic of Congo

In the digital age, the data exchanged within a company is a wealth of knowledge. The survival, growth and influence of a company in the short, medium and long term depend on it. Indeed, it is the lifeblood of any modern company. A companys operational and historical data contains strategic and operational knowledge of ever-increasing added value. The emergence of a new paradigm: big data. Today, the value of the data scattered throughout this mother of knowledge is calculated in billions of dollars, depending on its size, scope and area of intervention. With the rise of computer networks and distributed systems, the threats to these sensitive resources have steadily increased, jeopardizing the existence of the company itself by drying up production and losing the interest of customers and suppliers. These threats range from sabotage to bankruptcy. For several decades now, most companies have been using encryption algorithms to protect and secure their information systems against the threats and dangers posed by the inherent vulnerabilities of their infrastructure and the current economic climate. This vulnerability requires companies to make the right choice of algorithms to implement in their management systems. For this reason, the present work aims to carry out a comparative study of the reliability and effectiveness of symmetrical and asymmetrical cryptosystems, in order to identify one or more suitable for securing academic data in the DRC. The analysis of the robustness of commonly used symmetric and asymmetric cryptosystems will be the subject of simulations in this article.

Coordinated Rotor-Side Control Strategy for Doubly-FedWind Turbine under Symmetrical and Asymmetrical Grid Faults

In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of the doubly-fed generator is proposed.When the power grid voltage drops symmetrically,the generator approximate equation under steady-state conditions is no longer applicable.Considering the dynamic process of stator current excitation,according to the change of stator flux and the depth of voltage drop,the system can dynamically provide reactive power support for parallel nodes and suppress the rise of DC side voltage and rotor over-current.When the grid voltage drops asymmetrically,the positive and negative sequence components are separated in the rotating coordinate system.The doubly fed generator model is established to suppress the rotor positive sequence current and negative sequence current respectively.At the same time,the output voltage limit of the converter is discussed,and the reference value is adjusted within the allowable output voltage range.In order to adapt to the occurrence of different types of power grid faults and complex operating conditions,a fast switching module of fault type detection and rotor control mode is designed to detect the type of power grid faults and voltage drop depth in real time and switch the rotor side control mode dynamically.Finally,the simulation model of the doubly fed wind turbine is constructed in Matlab/Simulink.The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetric voltage drop of the power grid and identify the power grid fault type and provide the correct control strategy.

Shielding Effectiveness of Rural Concealed Communication Cable of Asymmetric/Symmetric Slots with Different Shapes

With the rural concealed communication cable as the study object, the shielding effectiveness of different slot shapes was analyzed by using LBEM （linear boundary element method）. The engineering example results showed that for twocore shielded cable, the coupling capacitance of trapezoid slots （asymmetric and symmetric） changed the most, followed by rectangular slots （asymmetric and symmetric）, and the changes of wedge slots were the smallest, but the change tenden- cies were consistent. In addition, with the increase of slot width of different slots, the coupling capacitance of tow-cored shielded cable showed small change.

Resistance Characteristic of High-speed Unstaggered Pentamaran Model with Variations of Symmetric and Asymmetric Hull Configurations

Pentamaran,a vessel with five hulls,can be an alternative for high-speed vessels due to its advantages,for instance,its excellent stability and seakeeping performance and broader deck space than an equivalent monohull with the same displacement.The destructive interference between the system of waves produced by the vessel’s hulls might benefit the reduction of power consumption.This study investigated a Wigley hull form pentamaran model with five asymmetric and symmetric hull config-urations and three variations of hull separation.The ship model was towed in conditions of fixed towing and calm water with Froude numbers(Fr)ranging from 0.55 to 1.00.A resistance analysis had been carried out to ensure proper comparison between the asymmetric and symmetric hull configurations.Results showed that total resistance coefficient of the asymmetries created different properties from the symmetries,that is,symmetries produced steadier trends than asymmetries.The hull separation variation caused a slight alteration in the total resistant coefficient(in magnitude)under the same configuration.Although not a single configuration outperformed the others in the entire range of Fr,three configurations were noteworthy as optimum models based on their Fr range.Moreover,a configuration of asymmetric hull with S/L=0.22 could generate a constant destructive interference throughout the investigated Fr range.

ADAPTIVE CONTROLLER AND ITS APPLICATION IN FORCE SYSTEM OF ASYMMETRIC CYLINDER CONTROLLED BY SYMMETRIC VALVE

Partial pressure, system vibration and asymmetric system dynamic performance exit in asymmetric cylinder controller by symmetric valve hydraulic system. To solve this problem in the force control system, model reference adaptive controller is designed using equilibrium point stability theory and output error equation polynomial. The reference model is selected in such a way that it meets the system dynamic performance. Hardware configuration of asymmetric cylinder controlled by asymmetric valve hydraulic system is replaced by intelligent control algorithm, thus the cost is lowered and easy to application. Simulation results demonstrate that the proposed adaptive control sheme has good adaptive ability and well solves asymmetric dynamic performance problem. The designed adaptive controller is fairly robust to load disturbance and system parameter variation.

A Comparative Study of the Performance of Symmetric and Asymmetric Mixed-conducting Membranes

According to the configuration,mixed-conducting membranes are classified as symmetric membranes and asymmetric membranes consisting of a thin dense layer and a porous support.In this study,these two kinds of SrCo0.4Fe0.5Zr0.1O3-δ oxide-based membranes were systematically compared in terms of oxygen permeability and chemical stability,and their differences were elucidated by means of the theoretical calculation.For the oxygen permeability,the asymmetric membrane was greater than the symmetric membrane due to the significant decrease of bulk diffusion resistance in the thin dense layer of the asymmetric membrane.In regard to the chemical stability,the increase of oxygen partial pressure on the asymmetric membrane surface at CH4 side produced the stable time of over 1032h in partial oxidation of methane at 1123K,while the symmetric membrane was only of 528h.This study demonstrated that the asymmetric membrane was a promising geometrical configuration for the practical application.

Determination of Asymmetric Dimethylarginine and Symmetric Dimethylarginine in Biological Samples of Mice Using LC/MS/MS

Herein, we present a novel method of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) determination within biological samples using protein precipitation and LC/MS/MS. Chromatographic separation of ADMA and SDMA was successfully performed using a silica column with optimized elution, or mobile phase, of 10 mM ammonium acetate buffer H2O/methanol/acetonitrile (20/30/45, v/v) at pH 4. The calibration ranges were 0.50 – 50.0 μg●mL-1, and good linearities were obtained for all compounds ( γ > 0.99). The intra- and inter-assay accuracies with recoveries and precisions at three concentration levels (i.e. 1.00, 5.00 and 25.0 μg●mL-1) were better than 86.9% and 7.36%, respectively. The analytical performance of the method was evaluated by determination of compounds in plasma, urine and tissues from male BALBc/J mice. For the first time, we were able to characterize the distribution of ADMA, SDMA and ADMA/SDMA in plasma, urine, brain, heart, kidneys, liver, lungs, pancreas and spleen. Additionally, we demonstrated that the ADMA/SDMA ratio in the brain was approximately 10-fold lower than all the other biological samples. Only 10 μL of plasma, 1 μL of urine and about 25 mg of tissues were required. These results suggest that the developed methodology was useful in ADMA and SDMA determination within biological samples.

Surface plasmon polaritons of symmetric and asymmetric metamaterial slabs

The p and s-polarized surface plasmon polaritons （SPPs） of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials： dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated.

Power Network Asymmetrical Faults Analysis Using Instantaneous Symmetrical Components

Although the application of Symmetrical Components to time-dependent variables was introduced by Lyon in 1954, for many years its application was essentially restricted to electric machines. Recently, thanks to its advantages, the Lyon transformation is also applied to power network calculation. In this paper, time-dependent symmetrical components are used to study the dynamic analysis of asymmetrical faults in a power system. The Lyon approach allows the calculation of the maximum values of overvoltages and overcurrents under transient conditions and to study network under non-sinusoidal conditions. Finally, some examples with longitudinal asymmetrical faults are illustrated.

Prediction of Symmetrical and Asymmetrical of Diurnal Global Solar Irradiance Distribution—New Approach

A simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis. It is expressed in terms of the length of the local day time td which is well defined in literatures on meteorological basis. The introduced distribution is also a function of the maximum value of the daily received irradiance qmax. which in turn is expressed in term of the solar constant. This renders the trial to be a closed system. Thus the obtained distribution is not a semi empirical one. Both cases of symmetrical and asymmetrical distributions for q(t) are considered. For its simplicity it can be easily integrated along the length of the day to get the daily totals of solar energy received by unit horizontal area. This is important for practical applications. Comparison between computed according to the present model and published experimental meteorological data in Barcelona (Spain), Hong Kong (China), Jeddah and Makkah (Saudi Arabia) is given as illustrative examples. Better fitting relative to the published trials for the same locations are obtained. The introduced model itself gives good fitting for the intermediate intervals points of the local day time which is the more effective region. The estimated relative error is 12% for Hong Kong, and it is 7% for Barcelona, Jeddah and Makah.

Testing Bifacial PV Cells in Symmetric and Asymmetric Concentrating CPC Collectors

Bifacial PV cells have the capacity to produce solar electricity from both sides and, thus, amongst other advantages, allow a significantly increase both in peak and annual power output while utilizing the same amount of silicone. According to the manufacturer, the bifacial cells are around 1.3 times more expensive than the single-sided cells. This way, bifacial PV cells can effectively reduce the cost of solar power for certain applications. Today, the most common application for these cells is in stationary vertical collectors which are exposed to sunlight from both sides, as the relative position of the sun changes throughout the day. Another possible application is to utilize these cells in concentrating collectors. Three test prototypes utilizing bifacial PV cells were built. The initial two prototypes were built for indoor testing and differed only in geometry of the reflector, one being asymmetric and the other symmetric. Both prototypes were evaluated in an indoor solar simulator. Both reflector designs yielded positive electrical performance results and similar efficiencies from both sides of the cell were achieved. However, lower fill factor than expected was achieved for both designs when compared to the single cell tests. The results are discussed and suggestions for further testing are presented. A third prototype was built in order to perform outdoor evaluations. This prototype utilized a bifacial PV cells string laminated in silicone enclosed between 2 standard glass panes and a collector box with an asymmetric CPC concentrator. The prototype peak electrical efficiency and temperature dependence were evaluated. A comparison between the performance of the bottom and top sides of the asymmetric collector is also presented. Additionally, the incidence modifier angle (IAM) is also briefly discussed.

Two Layer Symmetric Cryptography Algorithm for Protecting Data from Attacks

Many organizations have insisted on protecting the cloud server from the outside,although the risks of attacking the cloud server are mostly from the inside.There are many algorithms designed to protect the cloud server from attacks that have been able to protect the cloud server attacks.Still,the attackers have designed even better mechanisms to break these security algorithms.Cloud cryptography is the best data protection algorithm that exchanges data between authentic users.In this article,one symmetric cryptography algorithm will be designed to secure cloud server data,used to send and receive cloud server data securely.A double encryption algorithm will be implemented to send data in a secure format.First,the XOR function will be applied to plain text,and then salt technique will be used.Finally,a reversing mechanism will be implemented on that data to provide more data security.To decrypt data,the cipher text will be reversed,salt will be removed,andXORwill be implemented.At the end of the paper,the proposed algorithm will be compared with other algorithms,and it will conclude how much better the existing algorithm is than other algorithms.

Reducing laser beam fluence and intensity fluctuations in symmetric and asymmetric compressors

All space-time coupling effects arising in an asymmetric optical compressor consisting of two non-identical pairs of diffraction gratings are described analytically.In each pair,the gratings are identical and parallel to each other,whereas the distance between the gratings,the groove density and the angle of incidence are different in different pairs.It is shown that the compressor asymmetry does not affect the far-field fluence and on-axis focal intensity.The main distinctive feature of the asymmetric compressor is spatial noise lagging behind or overtaking the main pulse in proportion to the transverse wave vector.This results in a degraded contrast but reduces beam fluence fluctuations at the compressor output.Exact expressions are obtained for the spectrum of fluence fluctuations and fluence root mean square that depends only on one parameter characterizing compressor asymmetry.The efficiency of small-scale self-focusing suppression at subsequent pulse post-compression is estimated.

Basic Functions for Computational Implementation of the Box-Cox Symmetric Class of Distributions

A class of distributions called Box-Cox symmetric was proposed for random variables with asymmetric distributions. This class allows through its structure an interpretation of the parameters in terms of quantiles (in particular, the median), relative dispersion and skewness. This study presents the initial results of the computational development of basic functions of each of the distributions that make up the Box-Cox symmetric class. Four functions have been developed to compose a routine in software R up to now. These functions are related to random numbers generation, probability density function, cumulative distribution function, and quantile function associated to a given probability. Examples of implemented functions were presented. The gamlss routine was used to check the performance of developed functions.

用户恶意跨域数据安全加密共享算法仿真

在跨域数据共享场景下,涉及到多个组织或多个域的用户参与,为了保证数据安全,避免隐私信息泄露,提出了支持恶意用户追踪的跨域数据安全共享算法。将基于密文策略的属性基加密方法与白盒追踪算法和黑盒追踪算法结合。设计恶意用户追踪机制,实现对恶意用户的有效追踪。将对称加密算法和非对称加密算法相结合,生成公钥、私钥和密钥,对数据展开加解密处理,实现跨域数据安全共享。实验结果表明,所提算法的数据安全共享效果较高,在不同实验环境下均能够保持较低的内存,且信息熵较高,能够确保数据的安全性。

姚家平水利枢纽工程钢岔管结构型式选择与CFD研究

结合姚家平水利枢纽工程的总体布置,对主电站引水系统对称Y形和非对称Y形月牙肋钢岔管两种结构型式分别进行了三维有限元应力分析和CFD三维流场计算。计算结果表明:对称岔管两腰部位应力分布均匀,肋板尺寸较小;但在主支锥管相贯线内表面A点附近出现较大的应力集中现象,因此对称岔管满足强度所需的管壁厚度大于非对称岔管。在水力学方面,非对称岔管两支管的水头损失不相等,其中与主管同轴线的直支管水头损失最小,斜支管水头损失最大,但没超过对称岔管的0.358 m,说明从岔管部位水头损失和水流流态上看,非对称岔管也稍优于对称Y形岔管。综合考虑岔管结构和水力学特性以及工程地形等因素,建议姚家平水利枢纽工程中主电站引水发电系统选择非对称Y形岔管布置方案。

可搜索加密研究综述

为了有效解决数据隐私保护和安全搜索等问题,可搜索加密技术应时而生。可搜索加密是一种保护数据隐私的加密技术,允许在加密的状态下进行搜索和查询。可搜索加密的研究主要包括对称可搜索加密和非对称可搜索加密等,其基本原理包括对关键词进行编码和加密,设计相应的索引结构和搜索算法。可搜索加密技术在云计算、医疗健康、金融和物联网等领域具有广泛的应用潜力。研究者致力于提供效率更高、安全性更好、扩展性更强的可搜索加密方案。介绍了可搜索加密的相关研究历史以及2种可搜索加密技术,从安全性和关键词猜测攻击分析了可搜索加密技术的实用性,还指出了该领域存在的亟需解决的问题和今后的研究方向,在推进可搜索加密的进一步研究方面发挥了作用。

匀称型和非匀称型足月小于胎龄儿生命早期的线性生长模式

目的 分析匀称型和非匀称型足月小于胎龄儿(small for gestational age,SGA)0~1岁的线性生长模式,为SGA的早期生长监测提供参考依据。方法 采用前瞻性队列研究的方法,选取2020年1月1日至2022年1月1日于潍坊医学院附属医院产科分娩的健康足月SGA为研究对象。根据出生重量指数将研究对象分为匀称型和非匀称型SGA,其线性生长模式采用身长的生长速度、生长水平的变化、追赶生长、减速生长及生长迟缓等指标来综合反映,并进行组间比较。结果 共纳入135名足月SGA,其中匀称型SGA 38名、非匀称型SGA 97名。两组比较结果显示,非匀称型SGA的身长与年龄别身长Z评分在生长水平上相较于匀称型SGA处于优势,匀称型SGA的生长速度更快,两者比较差异均具有统计学意义(均P <0.05)。生命早期匀称型SGA出现追赶生长的发生率更高(P <0.05),至1岁时趋近非匀称型SGA的生长水平(P> 0.05)。非匀称型SGA不仅出现减速生长的发生率高于匀称型SGA,且出现超重或肥胖的发生率亦高,达到15.46%,两者比较差异均具有统计学意义(均P <0.05)。结论 匀称型SGA生命早期的线性生长模式更理想,非匀称型SGA容易出现生长失衡(减速生长、生长迟缓、超重或肥胖),更需要引起临床医生的重视。

高压选相断路器T100a试验电流和瞬态恢复电压的计算

相对于常规高压断路器,选相断路器的T100a试验的大半波电流非对称度增大,导致IEC 62271-101:2021附录A、E提供的电流和瞬态恢复电压(TRV)参数不再适用。为了快速精确地计算这些参数,文中提出了以短路电流对称分量为基础计算电流参数,通过时域分析获得TRV修正系数的方法,公式简单、灵活性好,适用范围广。其计算结果与传统公式计算值保持一致,并被IEC WG67认可,包含在IEC TS 62271-319(已通过DTS投票)附录N中。

3D打印负压吸盘个体化治疗75例儿童漏斗胸效果

目的:探讨3D打印负压吸盘个体化治疗漏斗胸患儿的治疗效果,并分析3D打印技术在对称型和非对称型漏斗胸治疗中的可行性。方法:回顾性分析2020年3月~2022年4月福州儿童医院收治的通过3D打印负压吸盘个体化治疗的漏斗胸患儿75例的临床资料,包括年龄、性别、Haller指数、漏斗胸深度、横径、纵径以及使用过程中出现的相关不良反应等,通过3D扫描获得使用前后漏斗部各项指标,对使用前后各项指标进行统计学分析,评价其临床治疗效果。结果:根据纳入标准和排除标准共75例患儿被纳入研究,其中男52例(69.33%),女23例(30.67%);年龄平均为(5.57±3.66)岁。75例患者治疗后漏斗部凹陷横径、凹陷纵径、凹陷深度、Haller指数均低于治疗前,差异具有统计学意义(P<0.05);其中44例对称型和31例非对称型漏斗胸患儿治疗后对称型漏斗部凹陷横径、凹陷纵径、凹陷深度、Haller指数也均低于治疗前,差异具有统计学意义(P<0.05)。矫形效果评价中,优秀1例,良好60例,一般14例,优良率高达81.33%。大部分患儿家属对诊疗效果表示满意(89.33%)。干预过程中出现相关不良反应较轻,多无需特殊干预。结论:3D打印负压吸盘个体化在治疗对称型和非对称型漏斗胸患儿均具有良好治疗效果,具有较好的可行性。