High Linearity Millimeter Wave Power Amplifiers with Novel Linearizer Techniques

Millimeter-wave communications have experienced phenomenal growth in recent years when limited frequency spectrum is occupied by the ever-developing communication services. The power amplifier, as the key component in the transmitter/receiver module of communication systems, affects performance of the whole system directly and receives much attention. For minimized distortion and optimum system performance, the non-constant en- velope modulation schemes used in communication systems have challenging requirements on linearity. As linearity is related to communication quality directly, several linearization techniques, such as predistortion and feedforward, are applied to power amplifier design. Predistortion method has the advantages over other techniques in relatively simple struc- ture and reasonable linearity improvement. But current predistortion circuits have quite limited performance improvement and relatively large insertion loss, which indicate the need for further research. In most of millimeter-wave amplifier design, great effort has been spent on output power or gain, while linearity is often ignored. As almost all the predistortion circuits operate at the RF frequencies, the linearized millimeter-wave com- munication circuit is still relatively immature and very challenging. This project is dedicated to solve the linearity problem faced by millimeter-wave power amplifier in communication systems, which lacks of e®ective techniques in this field. Linearity improvement with the predistortion method will be the key issue in this project and some original ideas for predistortion circuit design will be applied to millimeter-wave amplifiers. In this thesis, several predistortion circuits with novel structure were proposed, which provide a new approach for linearity improvement for millimeter-wave power am- plifier. A millimeter-wave power ampli¯er for LMDS applications built on GaAs pHEMT technology was developed to a high engineering standard, which works as the test bench for linearization. Actual operation and parasitic elements at tens of gigahertz have been taken into consideration during the design. Firstly, two novel predistorter structures based on the amplifier were proposed, one is based on an amplifier with a fixed bias circuit and the other is based on an amplifier with a nonlinear signal dependant bias circuit. These novel structures can improve the linearity while improving other metrics simultaneously, which can effectively solve the problem of insertion loss faced by the conventional structures. Besides this, an original predistortion circuit design methodology derived from frequency to signal amplitude transformation was proposed. Based on this methodology, several transfer functions were proposed and related predistortion circuits were built to linearize the power amplifier. As this methodology is quite different from the traditional approach, it can improve the linearity signifficantly while other metrics are affected slightly and has a broad prospect for application

Serious Game for Fire Evacuation

Fire safety for buildings has been of increasing concern due to the increase in occupant density in modern-day infrastructures. Efforts have been made by civil engineers to reduce loss in building fire accidents. For example, building codes have been refined to reduce the potential damage caused by fire by enforcing installation of fire detectors, alarm system, ventilation system, and sprinkler system. In addition, current building codes regulate the number of exits as well as the widths and heights of exits to allow an efficient evacuation process if the fire goes out of control. However the fire evacuation training aspect of fire safety is relatively immature. The fire evacuation process is still trained by carrying out traditional fire drills. However, the value of traditional fire drills has been questioned. Traditional fire evacuation drills fail to present a realistic fire environment to the participants. Traditional fire drills fail to raise enough seriousness for the participants since in most cases participants are informed about the drills beforehand. The cost of conducting these traditional fire drills can also be very high. Motivated by the problems faced by traditional fire drills, this research explores a new approach to more effectively and economically train people regarding the fire evacuation process. The new approach is to use a video game to train people for fire evacuation. The whole idea of using games for training and educational purposes falls under the concept of Serious Gaming, which has shown auspicious results in fields of military training, medical training, pilot training, and so on. In the virtual game environment, the fire environment can be simulated and rendered to the players. Doing so can allow the players to experience a more realistic fire environment and hence better prepare them for what to do in response to fire accidents. By setting a proper rewarding system, the game can motivate the players to treat the training more seriously. Also, since the training is carried out in the form of a game, it is more engaging and less costly. Currently, the game has been developed to render smoke and control the movement of agents. In order to make the game environment more realistic, the smoke is simulated and rendered using fire dynamics, and the agent movement is controlled by appropriate pedestrian models. It is worth mentioning that pedestrian modeling is still a relatively immature field of science and this game also serves as a tool for collecting and analyzing data for pedestrian models

Random structural dynamic response analysis under random excitation

A numerical procedure to compute the mean and covariance matrix of the random response of A numerical procedure to compute the mean and covariance matrix of the random response of stochastic structures modeled by FE models is presented. With Gegenbauer polynomial approximation, the calculation of dynamic response of random parameter system is transformed into an equivalent certainty expansion order system’s response calculation. Non- stationary, non-white, non-zero mean, Gaussian distributed excitation is represented by the well known Karhunen-Loeve (K-L) expansion. The Precise Integration Method is employed to obtain the K-L decomposition of the non- stationary filtered white noise random excitation. A accurate result is obtained by small amount of K-L vectors with the vector characteristic of energy concentration, especially for the small band-width excitation. Correctness of the method is verified by the simulations. The effects to the response mean square value by different probability density functions of random parameters with the same variable coefficient are studied, and a conclusion is drawn that it is inappropriate to approximate other types of probability distribution by normal distribution

Fluorescence studies on the interaction of a synthetic signal peptide and its analog with liposomes

AbstractThe N-terminal signal sequence of glucitol permease of Escherichia coli (Gut22: MIETITHGAEWFIGLFQKGGEC) and its analog (Gut22Ana: MIETITPGAVWFIGLFQKGGEC) were synthesized. The analog had a Pro residue substituted for the His at the 7th position of Gut22 and a Val residue substituted for the Glu at the 10th position. Previous studies indicated that due to its structural rigidity, the interaction of Gut22Ana with lipid bilayer was much weaker than that of Gut22 (Wang, Q.D., Cui, D.F. and Lin, Q.S. (1996) Science in China (Series C) 39, 395–405). To further probe the location of the tryptophan residues of the peptides in lipid bilayer, the membrane penetration depth of the tryptophan residue of Gut22 was measured using spin-labeled phospholipids, and fluorescence quenching of the peptides by iodide and acrylamide in the presence and absence of phosphatidylserine/phosphatidylcholine liposomes were also studied. Fluorescent labeling of the peptides enabled the study of their association with membrane by fluorospectrophotometry. In the presence of liposomes, the peptides were protected from reaction with chymotrypsin, indicating that the peptide incorporated into the membrane. However, dithionite, which acts external to the membrane, reacted with the peptide, showing that the peptides did not translocate across lipid bilayer spontaneously

Homomorphic Polynomial Public Key Cryptography for Quantum-secure Digital Signature

In their 2022 study, Kuang et al. introduced Multivariable Polynomial Public Key (MPPK) cryptography, leveraging the inversion relationship between multiplication and division for quantum-safe public key systems. They extended MPPK into Homomorphic Polynomial Public Key (HPPK), employing homomorphic encryption for large hidden ring operations. Originally designed for key encapsulation (KEM), HPPK's security relies on homomorphic encryption of public polynomials. This paper expands HPPK KEM to a digital signature scheme, facing challenges due to the distinct nature of verification compared to decryption. To adapt HPPK KEM to digital signatures, the authors introduce an extension of the Barrett reduction algorithm, transforming modular multiplications into divisions in the verification equation over a prime field. The extended algorithm non-linearly embeds the signature into public polynomial coefficients, addressing vulnerabilities in earlier MPPK DS schemes. Security analysis demonstrates exponential complexity for private key recovery and forged signature attacks, considering ring bit length twice that of the prime field size.Comment: 16 pages, 1 figur

Experimental Study on the Mechanical Behaviors of PVA-ECC after Freeze-Thaw Cycles

yesIn order to study the mechanical behaviors of engineered cementitious composites (ECC) reinforced with various types of polyvinyl alcohol (PVA) fibers and different fiber volume fractions after the freeze-thaw cycles, the rapid freeze-thaw method was used to test the mass loss ratios, longitudinal relative dynamic elastic modulus, compressive strength and flexural strength. The results showed that specimens incurred more serious damage with the increasing of freeze-thaw cycles; however their performance would be improved by fiber type and dosage. Mass loss rate of JPA (specimen with 2% volume content of JP fiber) was lower than JPB (specimen with 1% volume content of JP fiber). Furthermore, the mass loss rate of JPB was lower than that of CPB (specimen with 1% volume content of CP fiber). The longitudinal relative dynamic elastic modulus of JPA was higher than that of JPB while the longitudinal relative dynamic elastic modulus of JPB was higher than that of CPB. In addition, the compressive strength and flexural strength decreased with the increasing of freeze-thaw cycles. Mechanical behaviors of specimens with fiber exhibited better strength than specimens without fiber. Based on the SL 211-2006 code for the design of hydraulic structures against ice and freezing action, JPA and JPB specimens are adequate for use in severe cold regions, while specimen CPA and CPB can be used in cold regions, specimen JPC only can be used in warm regions

Overexpression of BMI-1 Promotes Cell Growth and Resistance to Cisplatin Treatment in Osteosarcoma

Background: BMI-1 is a member of the polycomb group of genes (PcGs), and it has been implicated in the development and progression of several malignancies, but its role in osteosarcoma remains to be elucidated. Methodology/Principal Findings: In the present study, we found that BMI-1 was overexpressed in different types of osteosarcomas. Downregulation of BMI-1 by lentivirus mediated RNA interference (RNAi) significantly impaired cell viability and colony formation in vitro and tumorigenesis in vivo of osteosarcoma cells. BMI-1 knockdown sensitized cells to cisplatininduced apoptosis through inhibition of PI3K/AKT pathway. Moreover, BMI-1-depletion-induced phenotype could be rescued by forced expression of BMI-1 wobble mutant which is resistant to inhibition by the small interfering RNA (siRNA). Conclusions/Significance: These findings suggest a crucial role for BMI-1 in osteosarcoma pathogenesis

Homomorphic Polynomial Public Key Cryptography for Quantum-secure Digital Signature

In their 2022 study, Kuang et al. introduced the Multivariable Polynomial Public Key (MPPK) cryptography, a quantum-safe public key cryptosystem leveraging the mutual inversion relationship between multiplication and division. MPPK employs multiplication for key pair construction and division for decryption, generating public multivariate polynomials. Kuang and Perepechaenko expanded the cryptosystem into the Homomorphic Polynomial Public Key (HPPK), transforming product polynomials over large hidden rings using homomorphic encryption through modular multiplications. Initially designed for key encapsulation mechanism (KEM), HPPK ensures security through homomorphic encryption of public polynomials over concealed rings. This paper extends its application to a digital signature scheme. The framework of HPPK KEM can not be directly applied to the digital signatures dues to the different nature of verification procedure compared to decryption procedure. Thus, in order to use the core ideas of the HPPK KEM scheme in the framework of digital signatures, the authors introduce an extension of the Barrett reduction algorithm. This extension transforms modular multiplications over hidden rings into divisions in the verification equation, conducted over a prime field. The extended algorithm non-linearly embeds the signature into public polynomial coefficients, employing the floor function of big integer divisions. This innovative approach overcomes vulnerabilities associated with linear relationships of earlier MPPK DS schemes. The security analysis reveals exponential complexity for both private key recovery and forged signature attacks, taking into account that the bit length of the rings is twice that of the prime field size. The effectiveness of the proposed Homomorphic Polynomial Public Key Digital Signature (HPPK DS) scheme is illustrated through a practical toy example, showcasing its intricate functionality and enhanced security features