Greedy propagation policy for unstructured P2P worms employs the neighboring node list of each node in peer-to-peer （P2P） network to speed up the propagation of P2P worms. After describing the technique background o...Greedy propagation policy for unstructured P2P worms employs the neighboring node list of each node in peer-to-peer （P2P） network to speed up the propagation of P2P worms. After describing the technique background of P2P worms, the algorithm of greedy propagation is addressed. Simulating design for this novel propagation policy is also described. Then, the effects of the greedy propagation policy on spreading speed, convergence speed, and attacking traffic in static P2P worms are simulated and discussed. The primary experimental results show that the greedy propagation is harmful and can bring severe damages to P2P network.展开更多
The Guanshan Biota from the Cambrian Stage 4 Wulongqing Formation is a typical Burgess-shale type Lagerst？tte that had witnessed the Cambrian explosion. Here we report two new localities of the Guanshan Biota, which ...The Guanshan Biota from the Cambrian Stage 4 Wulongqing Formation is a typical Burgess-shale type Lagerst？tte that had witnessed the Cambrian explosion. Here we report two new localities of the Guanshan Biota, which is located at Baimei village, south of Kunming and Xinglong village, Wuding County, Yunnan Province respectively. Both localities produce soft-body fossils and several new taxa, e.g. a new species of palaeoscolecidans （Palaeoscolex xinglongensis sp. nov.） reported herein. The comparative study of the new species with similar form not only indicates that there is a diversification of palaeoscolecid species in Guanshan Biota, but also strengthens the ties between the older Chengjiang Biota and the younger Kaili Biota （and also the coeval Burgess Shale community）. Three paleoecological features, including high diversity, little disparity and richness of palaeoscolecid worms, are summarized as a case study to represent the differences between Guanshan and Chengjiang Biota.展开更多
Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly ...Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly analyzes and obtains the average delay for all peers in the whole transmitting process due to the limitation of network throughput, and then proposes a mathematical model for the propagation of passive worms over the unstructured P2P networks. The model mainly takes the effect of the network throughput into account, and applies a new healthy files dissemination-based defense strategy according to the file popularity which follows the Zipf distribution. The simulation results show that the propagation of passive worms is mainly governed by the number of hops, initially infected files and uninfected files. The larger the number of hops, the more rapidly the passive worms propagate. If the number of the initially infected files is increased by the attackers, the propagation speed of passive worms increases obviously. A larger size of the uninfected file results in a better attack performance. However, the number of files generated by passive worms is not an important factor governing the propagation of passive worms. The effectiveness of healthy files dissemination strategy is verified. This model can provide a guideline in the control of unstructured P2P networks as well as passive worm defense.展开更多
Instant messaging （IM） has become one of the most popular online communication tools among consumer and enterprise IM users. It provides instant message delivery, as well as convenient file transfer services. The in...Instant messaging （IM） has become one of the most popular online communication tools among consumer and enterprise IM users. It provides instant message delivery, as well as convenient file transfer services. The increasing popularity and functionalities of IM programs have made it increasingly attractive for attackers, especially for worm writers. IM contact list offers worm an easy way of finding potential victims so that the worm could achieve a surprising spreading speed. This paper first presents our experimental results of simulating IM worm propagation in the logical network defined by IM contact lists, which is reported to be a scale-free network. Then, the existing proposals for detecting and containing IM worm epidemics are discussed. At last, a new algorithm for this purpose is presented, which is based on the observation of the bi-directional nature of IM worm traffic, and its advantages and possible improvements in implementation are analyzed. The simulation results show the proposed algorithm is of significant effect on restricting IM worm propagation.展开更多
Viruses and worms have become so common that most computer users now accept them as a fact of life.This paper introduces the definitions and difference of the computer viruses and worms.Some main research problems abo...Viruses and worms have become so common that most computer users now accept them as a fact of life.This paper introduces the definitions and difference of the computer viruses and worms.Some main research problems about the computer viruses and worms in recent years are also summarized and discussed in detail.Finally the developing trend of the computer virus and worms is proposed.展开更多
The aim of the present study was to evaluate the efficacy of two commercial pour-on ivermectin formulations against intestinal parasites (IP), fleas and lice in naturally infested stray dogs. Eighteen crossbreed dogs ...The aim of the present study was to evaluate the efficacy of two commercial pour-on ivermectin formulations against intestinal parasites (IP), fleas and lice in naturally infested stray dogs. Eighteen crossbreed dogs with eggs of IP as well as adult fleas and lice were included in the trial. On day 0, the dogs were randomly divided into 3 groups of 6 animals each: a group receiving a single pour-on treatment with 0.5% ivermectin (500 mcg/kg), a group treated similarly with 0.2% iver-mectin (200 mg/kg), and a control group. Fecal and skin analyses were carried out on days 0, 7, 14, 21 and 28 to determine the reduction of eggs and the number of fleas and lice. Weight gain was also measured on day 28. On day 30, the dogs were humanely sacrificed in order to count adult IP. Efficacy was measured as the percentage of the reduction of eggs per gram fecal mass (EPGF), of adult IP, fleas and lice relative to the control group. For the eggs of IP, ivermectin at 0.5% showed an efficacy of 100% against ascarids and 79% against Ancylostoma caninum. ivermectin at 0.2% removed 90.2% of the ascarids and 50.4% of A. caninum. For adult IP, the efficacy of 0.5% iver-mectin against Toxocara canis and A. caninum was 100%, and for 0.2% ivermectin it was 62.4% and 76.4% for T. canis and A. caninum, respectively. Both compounds were 100% effective against lice and 96% and 71.1% efficacious against fleas, respectively. However, neither treatment was effective against Dypilidium caninum. Weight gain in treated dogs was statistically different from that of the controls (p < 0.05). We concluded that 0.5% pour-on ivermectin showed better efficacy than 0.2% pour-on ivermectin in the reduction of eggs and adult intestinal parasites and fleas;it was similarly efficacious against lice.展开更多
In this paper, we study worm dynamics in computer networks composed of many autonomous systems. A novel multigroup SIQR （susceptible-infected-quarantined-removed） model is proposed for computer worms by explicitly c...In this paper, we study worm dynamics in computer networks composed of many autonomous systems. A novel multigroup SIQR （susceptible-infected-quarantined-removed） model is proposed for computer worms by explicitly considering anti-virus measures and the network infrastructure. Then, the basic reproduction number of worm R0 is derived and the global dynamics of the model are established. It is shown that if R0 is less than or equal to 1, the disease-free equilibrium is globally asymptotically stable and the worm dies out eventually, whereas, if R0 is greater than 1, one unique endemic equilibrium exists and it is globally asymptotically stable, thus the worm persists in the network. Finally, numerical simulations are given to illustrate the theoretical results.展开更多
Along with the rapid development of social networks, social network worms have constituted one of the major internet security problems. The root of worm is the inevitable software vulnerability during the design and i...Along with the rapid development of social networks, social network worms have constituted one of the major internet security problems. The root of worm is the inevitable software vulnerability during the design and implementation process of software. So it is hard to completely avoid worms in the existing software engineering systems. Due to lots of bandwidth consumption, the patch cannot be transmitted simultaneously by the network administrator to all hosts. This paper studies how to prevent the propagation of social network worms through the immunization of key nodes. Unlike existing containment models for worm propagation, a novel immunization strategy is proposed based on network vertex influence. The strategy selects the critical vertices in the whole network. Then the immunization is applied on the selected vertices to achieve the maximal effect of worm containment with minimal cost. Different algorithms are implemented to select vertices. Simulation experiments are presented to analyze and evaluate the performance of different algorithms.展开更多
With the development and the application of many popular peer-to-peer （P2P） systems such as eMule and BitTorrent, worms probably employ the features of these P2P networks to put them at risk. Some features, such as ...With the development and the application of many popular peer-to-peer （P2P） systems such as eMule and BitTorrent, worms probably employ the features of these P2P networks to put them at risk. Some features, such as the local routing table and the application routing mechanism, are helpful to quickly distribute the P2P worms into the networks. This paper aims to give a comprehensive survey of P2P worms. The definition and the classification of P2P worms are discussed firstly. Then, the research and development of P2P worms, including experimental analysis, propagation modeling, and defensive approaches, are addressed and analyzed in detail.展开更多
Internet worm is harmful to network security,and it has become a research hotspot in recent years.A thorough survey on the propagation models and defense techniques of Internet worm is made in this paper.We first give...Internet worm is harmful to network security,and it has become a research hotspot in recent years.A thorough survey on the propagation models and defense techniques of Internet worm is made in this paper.We first give its strict definition and discuss the working mechanism.We then analyze and compare some repre-sentative worm propagation models proposed in recent years,such as K-M model,two-factor model,worm-anti-worm model（WAW）,firewall-based model,quarantine-based model and hybrid benign worm-based model,etc.Some typical defense techniques such as virtual honeypot,active worm prevention and agent-oriented worm defense,etc.,are also discussed.The future direction of the worm defense system is pointed out.展开更多
The clinical diagnosis of trichinellosis is difficult because its clinical manifestations are nonspecific.Detection of anti-Trichinella IgG by ELISA using T.spiralis muscle larval excretory-secretory(ES)antigens is th...The clinical diagnosis of trichinellosis is difficult because its clinical manifestations are nonspecific.Detection of anti-Trichinella IgG by ELISA using T.spiralis muscle larval excretory-secretory(ES)antigens is the most commonly used serological method for diagnosis of trichinellosis,but the main disadvantage is false negativity during the early stage of infection.There is an obvious window period between Trichinella infection and antibody positivity.During the intestinal stage of Trichinella infection,the ES antigens of intestinal worms(intestinal infective larvae and adults)are exposed to host’s immune system at the earliest time and elicit the production of specific anti-Trichinella antibodies.Anti-Trichinella IgG antibodies in infected mice were detectable by ELISA with ES antigens of intestinal worms as soon as 8-10 days post infection(dpi),but ELISA with muscle larval ES antigens did not permit detection of infected mice before 12 dpi.Therefore,the new early antigens from T.spiralis intestinal worms should be screened,identified and characterized for early serodiagnosis of trichinellosis.展开更多
The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can caus...The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can cause changes in cutting force/heat,resulting in affecting gear machining precision.Therefore,this paper studies the effect of different process parameters on gear machining precision.A multi-objective optimization model is established for the relationship between process parameters and tooth surface deviations,tooth profile deviations,and tooth lead deviations through the cutting speed,feed rate,and cutting depth of the worm wheel gear grinding machine.The response surface method(RSM)is used for experimental design,and the corresponding experimental results and optimal process parameters are obtained.Subsequently,gray relational analysis-principal component analysis(GRA-PCA),particle swarm optimization(PSO),and genetic algorithm-particle swarm optimization(GA-PSO)methods are used to analyze the experimental results and obtain different optimal process parameters.The results show that optimal process parameters obtained by the GRA-PCA,PSO,and GA-PSO methods improve the gear machining precision.Moreover,the gear machining precision obtained by GA-PSO is superior to other methods.展开更多
A type of novel biodegradable fibers,made from magnetic particles and the patient’s own blood,promises an immune-evading brain cancer therapy with minimal invasion.
The worm wheel whose undercutting characteristic is researched is a member of offsetting normal arc-toothed cylindrical worm drive.The tooth profile of the worm in its offsetting normal section is a circular arc.The n...The worm wheel whose undercutting characteristic is researched is a member of offsetting normal arc-toothed cylindrical worm drive.The tooth profile of the worm in its offsetting normal section is a circular arc.The normal vector used to calculate the first-type limit function is determined in the natural frame without the aid of the curvature parameter of worm helicoid.The first-type limit line is ascertained via solving the nonlinear equations iteratively.It is discovered that one first-type limit line exists on the tooth surface of worm wheel by numerical simulation,and such a line is normally located out of the meshing zone.Only one intersection point exists between the first and second-types of limit lines,and this point is a lubrication weak point.The undercutting mechanism is essentially that a part of the meshing zone near the conjugated line of worm tooth crest will come into the undercutting area and will be cut off during machining the worm wheel.The machining simulation verifies the correctness of undercutting mechanism.Moreover,a convenient and practical characteristic quantity is proposed to judge whether the undercutting exists in the whole meshing zone via computing the first-type limit function values on the worm tooth crest.展开更多
Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
长命,是自古以来人们的一种渴望。现在看来,人类在延续人的寿命方面的努力已经闪烁成功的曙光。本文告诉我们,科学家在虫子身上的试验,已经获得成功。就现在的科研成果而言,具有实践意义的内容是:Experiments haveshown that lifetime l...长命,是自古以来人们的一种渴望。现在看来,人类在延续人的寿命方面的努力已经闪烁成功的曙光。本文告诉我们,科学家在虫子身上的试验,已经获得成功。就现在的科研成果而言,具有实践意义的内容是:Experiments haveshown that lifetime low-calorie diets,for instance,can help mice live longer thannormal.另一条却是无法实现的:…reproduction somehow shortens lifespanand that animals whose reproductive systems are shut down may live longer.展开更多
To validate the protective efficacy against schistosomiasis by immunization with cells from juvenile Schistosoma japonicum in a murine model; to analyze possible factors related to protection, in this study, two indep...To validate the protective efficacy against schistosomiasis by immunization with cells from juvenile Schistosoma japonicum in a murine model; to analyze possible factors related to protection, in this study, two independent repeated vaccination trials were performed. After three subcutaneous vaccinations, in trial one, in the absence of adjuvant, primary juvenile worm cells (pJCs) from S. japonicum induced remarkable average reductions in worm burden (54.3%), liver eggs per gram (LEPG) load (59.8%) as well as egg granulomas size (66.5%) compared to PBS control group (P【0.01), which were significantly higher than those elicited by fractions of juvenile worm cells (JCFs) or fractions of juvenile worms (JWFs) (P【0.05). Non-cell components of worms (WNCs) showed no significant protection. In trial two, compared to PBS control group, significant protective effect was also observed for cultured juvenile worm cells (cJCs) from S. japonicum with 58.4% worm reduction; 68.1% LEPG reduction (P【0.01). However, cultured adult worms cells (cACs) showed significantly higher worm burden (P【0.05); egg burden (P【0.01) when compared to cJCs. Immunological analysis of trial two revealed that cJCs engendered a Th1-biased mixed Th1/Th2 type of immune response while cACs elicited a Th2-type response. Our data indicated that immunization with both primary; cultured cells from S. japonicum juvenile worms provided high immunoprotection, for which the physical character of immunogens, stage-specific parasite; the type of immune response induced might be responsible, suggesting that vaccination with whole cells from S. japonicum larvae is a promising approach to produce protective immunity against schistosomiasis.展开更多
Interaction of antiworms with a worm population of e.g. hosts of worm infected and hosts of antiworm infected must be considered as a dynamic process. This study is an attempt for the first time to understand how intr...Interaction of antiworms with a worm population of e.g. hosts of worm infected and hosts of antiworm infected must be considered as a dynamic process. This study is an attempt for the first time to understand how introduction of antiworm affects the dynamic of network worm propagation. In this paper, we create a mathematical model (SIAR model) using ordinary differential equations to describe the interaction of worms and antiworms. Although idealized, the model demonstrates how the combination of a few proposed nonlinear interaction rules between antiworms and worms is able to generate a considerable variety of different kinds of responses. Taking the Blaster and Nachi worms as an example, we give a brief analysis for designing a practical antiworm system. To the best of our knowledge, there is no model for the spread of an antiworm that employs the passive scan and the finite lifetime and we believe that this is the first attempt on understanding the interaction between worms and antiworms.展开更多
基金supported by the National Natural Science Foundation of China under Grant No. 60873075
文摘Greedy propagation policy for unstructured P2P worms employs the neighboring node list of each node in peer-to-peer （P2P） network to speed up the propagation of P2P worms. After describing the technique background of P2P worms, the algorithm of greedy propagation is addressed. Simulating design for this novel propagation policy is also described. Then, the effects of the greedy propagation policy on spreading speed, convergence speed, and attacking traffic in static P2P worms are simulated and discussed. The primary experimental results show that the greedy propagation is harmful and can bring severe damages to P2P network.
基金financially supported by the 973 Project of the Ministry of Science and Technology of China(Grant 2013CB837100)the National Natural Science Foundation of China(Grant 41222014,41172023,41621003,41102012)+4 种基金the National Program for Support of Top-notch Young Professionalsfinancial support from the Ministry of Education of China for Changjiang Scholarthe Program of Introducing Talents of Discipline to Universities(P201102007,W20136100061)Shaanxi Bureau of Science and Technology(FJ11366)Young Talents of Northwest University
文摘The Guanshan Biota from the Cambrian Stage 4 Wulongqing Formation is a typical Burgess-shale type Lagerst？tte that had witnessed the Cambrian explosion. Here we report two new localities of the Guanshan Biota, which is located at Baimei village, south of Kunming and Xinglong village, Wuding County, Yunnan Province respectively. Both localities produce soft-body fossils and several new taxa, e.g. a new species of palaeoscolecidans （Palaeoscolex xinglongensis sp. nov.） reported herein. The comparative study of the new species with similar form not only indicates that there is a diversification of palaeoscolecid species in Guanshan Biota, but also strengthens the ties between the older Chengjiang Biota and the younger Kaili Biota （and also the coeval Burgess Shale community）. Three paleoecological features, including high diversity, little disparity and richness of palaeoscolecid worms, are summarized as a case study to represent the differences between Guanshan and Chengjiang Biota.
基金National Natural Science Foundation of China (No.60633020 and No. 90204012)Natural Science Foundation of Hebei Province (No. F2006000177)
文摘Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly analyzes and obtains the average delay for all peers in the whole transmitting process due to the limitation of network throughput, and then proposes a mathematical model for the propagation of passive worms over the unstructured P2P networks. The model mainly takes the effect of the network throughput into account, and applies a new healthy files dissemination-based defense strategy according to the file popularity which follows the Zipf distribution. The simulation results show that the propagation of passive worms is mainly governed by the number of hops, initially infected files and uninfected files. The larger the number of hops, the more rapidly the passive worms propagate. If the number of the initially infected files is increased by the attackers, the propagation speed of passive worms increases obviously. A larger size of the uninfected file results in a better attack performance. However, the number of files generated by passive worms is not an important factor governing the propagation of passive worms. The effectiveness of healthy files dissemination strategy is verified. This model can provide a guideline in the control of unstructured P2P networks as well as passive worm defense.
基金Supported by the National Natural Science Foundation of China (60573136)
文摘Instant messaging （IM） has become one of the most popular online communication tools among consumer and enterprise IM users. It provides instant message delivery, as well as convenient file transfer services. The increasing popularity and functionalities of IM programs have made it increasingly attractive for attackers, especially for worm writers. IM contact list offers worm an easy way of finding potential victims so that the worm could achieve a surprising spreading speed. This paper first presents our experimental results of simulating IM worm propagation in the logical network defined by IM contact lists, which is reported to be a scale-free network. Then, the existing proposals for detecting and containing IM worm epidemics are discussed. At last, a new algorithm for this purpose is presented, which is based on the observation of the bi-directional nature of IM worm traffic, and its advantages and possible improvements in implementation are analyzed. The simulation results show the proposed algorithm is of significant effect on restricting IM worm propagation.
基金Supported by the National Natural Science Foundation of China under Grant No.60373087,60473023,90104005
文摘Viruses and worms have become so common that most computer users now accept them as a fact of life.This paper introduces the definitions and difference of the computer viruses and worms.Some main research problems about the computer viruses and worms in recent years are also summarized and discussed in detail.Finally the developing trend of the computer virus and worms is proposed.
文摘The aim of the present study was to evaluate the efficacy of two commercial pour-on ivermectin formulations against intestinal parasites (IP), fleas and lice in naturally infested stray dogs. Eighteen crossbreed dogs with eggs of IP as well as adult fleas and lice were included in the trial. On day 0, the dogs were randomly divided into 3 groups of 6 animals each: a group receiving a single pour-on treatment with 0.5% ivermectin (500 mcg/kg), a group treated similarly with 0.2% iver-mectin (200 mg/kg), and a control group. Fecal and skin analyses were carried out on days 0, 7, 14, 21 and 28 to determine the reduction of eggs and the number of fleas and lice. Weight gain was also measured on day 28. On day 30, the dogs were humanely sacrificed in order to count adult IP. Efficacy was measured as the percentage of the reduction of eggs per gram fecal mass (EPGF), of adult IP, fleas and lice relative to the control group. For the eggs of IP, ivermectin at 0.5% showed an efficacy of 100% against ascarids and 79% against Ancylostoma caninum. ivermectin at 0.2% removed 90.2% of the ascarids and 50.4% of A. caninum. For adult IP, the efficacy of 0.5% iver-mectin against Toxocara canis and A. caninum was 100%, and for 0.2% ivermectin it was 62.4% and 76.4% for T. canis and A. caninum, respectively. Both compounds were 100% effective against lice and 96% and 71.1% efficacious against fleas, respectively. However, neither treatment was effective against Dypilidium caninum. Weight gain in treated dogs was statistically different from that of the controls (p < 0.05). We concluded that 0.5% pour-on ivermectin showed better efficacy than 0.2% pour-on ivermectin in the reduction of eggs and adult intestinal parasites and fleas;it was similarly efficacious against lice.
基金Project supported by the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2010526)the Six Projects Sponsoring Talent Summits of Jiangsu Province, China (Grant No. SJ209006)+2 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20103223110003)the Ministry of Education Research in the Humanities and Social Sciences Planning Fund of China (Grant No. 12YJAZH120)the Graduate Student Innovation Research Project of Jiangsu Province, China (Grant Nos. CXLX11 0417 and CXLX11 0404)
文摘In this paper, we study worm dynamics in computer networks composed of many autonomous systems. A novel multigroup SIQR （susceptible-infected-quarantined-removed） model is proposed for computer worms by explicitly considering anti-virus measures and the network infrastructure. Then, the basic reproduction number of worm R0 is derived and the global dynamics of the model are established. It is shown that if R0 is less than or equal to 1, the disease-free equilibrium is globally asymptotically stable and the worm dies out eventually, whereas, if R0 is greater than 1, one unique endemic equilibrium exists and it is globally asymptotically stable, thus the worm persists in the network. Finally, numerical simulations are given to illustrate the theoretical results.
基金supported by Fundamental Research Funds of the Central Universities under Grant no. N120317001 and N100704001Program for New Century Excellent Talents in University (NCET13-0113)+1 种基金Natural Science Foundation of Liaoning Province of China under Grant no. 201202059Program for Liaoning Excellent Talents in University under LR2013011
文摘Along with the rapid development of social networks, social network worms have constituted one of the major internet security problems. The root of worm is the inevitable software vulnerability during the design and implementation process of software. So it is hard to completely avoid worms in the existing software engineering systems. Due to lots of bandwidth consumption, the patch cannot be transmitted simultaneously by the network administrator to all hosts. This paper studies how to prevent the propagation of social network worms through the immunization of key nodes. Unlike existing containment models for worm propagation, a novel immunization strategy is proposed based on network vertex influence. The strategy selects the critical vertices in the whole network. Then the immunization is applied on the selected vertices to achieve the maximal effect of worm containment with minimal cost. Different algorithms are implemented to select vertices. Simulation experiments are presented to analyze and evaluate the performance of different algorithms.
基金supported by the National Natural Science Foundation of China under Grant No. 60873075
文摘With the development and the application of many popular peer-to-peer （P2P） systems such as eMule and BitTorrent, worms probably employ the features of these P2P networks to put them at risk. Some features, such as the local routing table and the application routing mechanism, are helpful to quickly distribute the P2P worms into the networks. This paper aims to give a comprehensive survey of P2P worms. The definition and the classification of P2P worms are discussed firstly. Then, the research and development of P2P worms, including experimental analysis, propagation modeling, and defensive approaches, are addressed and analyzed in detail.
基金supported by the Research Fund for the National Committee of China under Grant No. 05XN09
文摘Internet worm is harmful to network security,and it has become a research hotspot in recent years.A thorough survey on the propagation models and defense techniques of Internet worm is made in this paper.We first give its strict definition and discuss the working mechanism.We then analyze and compare some repre-sentative worm propagation models proposed in recent years,such as K-M model,two-factor model,worm-anti-worm model（WAW）,firewall-based model,quarantine-based model and hybrid benign worm-based model,etc.Some typical defense techniques such as virtual honeypot,active worm prevention and agent-oriented worm defense,etc.,are also discussed.The future direction of the worm defense system is pointed out.
基金This work was supported by the National Natural Science Foundation of China(no.81572024 and 81672043)The funders had no role in study design,data collection and analysis,decision to publish,or preparation of the manuscript.
文摘The clinical diagnosis of trichinellosis is difficult because its clinical manifestations are nonspecific.Detection of anti-Trichinella IgG by ELISA using T.spiralis muscle larval excretory-secretory(ES)antigens is the most commonly used serological method for diagnosis of trichinellosis,but the main disadvantage is false negativity during the early stage of infection.There is an obvious window period between Trichinella infection and antibody positivity.During the intestinal stage of Trichinella infection,the ES antigens of intestinal worms(intestinal infective larvae and adults)are exposed to host’s immune system at the earliest time and elicit the production of specific anti-Trichinella antibodies.Anti-Trichinella IgG antibodies in infected mice were detectable by ELISA with ES antigens of intestinal worms as soon as 8-10 days post infection(dpi),but ELISA with muscle larval ES antigens did not permit detection of infected mice before 12 dpi.Therefore,the new early antigens from T.spiralis intestinal worms should be screened,identified and characterized for early serodiagnosis of trichinellosis.
基金Projects(U22B2084,52275483,52075142)supported by the National Natural Science Foundation of ChinaProject(2023ZY01050)supported by the Ministry of Industry and Information Technology High Quality Development,China。
文摘The gears of new energy vehicles are required to withstand higher rotational speeds and greater loads,which puts forward higher precision essentials for gear manufacturing.However,machining process parameters can cause changes in cutting force/heat,resulting in affecting gear machining precision.Therefore,this paper studies the effect of different process parameters on gear machining precision.A multi-objective optimization model is established for the relationship between process parameters and tooth surface deviations,tooth profile deviations,and tooth lead deviations through the cutting speed,feed rate,and cutting depth of the worm wheel gear grinding machine.The response surface method(RSM)is used for experimental design,and the corresponding experimental results and optimal process parameters are obtained.Subsequently,gray relational analysis-principal component analysis(GRA-PCA),particle swarm optimization(PSO),and genetic algorithm-particle swarm optimization(GA-PSO)methods are used to analyze the experimental results and obtain different optimal process parameters.The results show that optimal process parameters obtained by the GRA-PCA,PSO,and GA-PSO methods improve the gear machining precision.Moreover,the gear machining precision obtained by GA-PSO is superior to other methods.
文摘A type of novel biodegradable fibers,made from magnetic particles and the patient’s own blood,promises an immune-evading brain cancer therapy with minimal invasion.
基金Projects(52205069,52075083,52304049)supported by the National Natural Science Foundation of ChinaProject(2021-BS-164)supported by the Liaoning Province Doctoral Research Startup Fund,China+2 种基金Project(LJKZ0264)supported by the Science and Technology Research Projects of Education Department of Liaoning Province,ChinaProject(G2022003010L)supported by the High-end Foreign Experts Recruitment Plan of ChinaProject(E2021203095)supported by the Natural Science Foundation for Young Scholars of Hebei Province,China。
文摘The worm wheel whose undercutting characteristic is researched is a member of offsetting normal arc-toothed cylindrical worm drive.The tooth profile of the worm in its offsetting normal section is a circular arc.The normal vector used to calculate the first-type limit function is determined in the natural frame without the aid of the curvature parameter of worm helicoid.The first-type limit line is ascertained via solving the nonlinear equations iteratively.It is discovered that one first-type limit line exists on the tooth surface of worm wheel by numerical simulation,and such a line is normally located out of the meshing zone.Only one intersection point exists between the first and second-types of limit lines,and this point is a lubrication weak point.The undercutting mechanism is essentially that a part of the meshing zone near the conjugated line of worm tooth crest will come into the undercutting area and will be cut off during machining the worm wheel.The machining simulation verifies the correctness of undercutting mechanism.Moreover,a convenient and practical characteristic quantity is proposed to judge whether the undercutting exists in the whole meshing zone via computing the first-type limit function values on the worm tooth crest.
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
文摘长命,是自古以来人们的一种渴望。现在看来,人类在延续人的寿命方面的努力已经闪烁成功的曙光。本文告诉我们,科学家在虫子身上的试验,已经获得成功。就现在的科研成果而言,具有实践意义的内容是:Experiments haveshown that lifetime low-calorie diets,for instance,can help mice live longer thannormal.另一条却是无法实现的:…reproduction somehow shortens lifespanand that animals whose reproductive systems are shut down may live longer.
基金Supported by the National Natural Science Foundation of China (Grant No. 30570952)
文摘To validate the protective efficacy against schistosomiasis by immunization with cells from juvenile Schistosoma japonicum in a murine model; to analyze possible factors related to protection, in this study, two independent repeated vaccination trials were performed. After three subcutaneous vaccinations, in trial one, in the absence of adjuvant, primary juvenile worm cells (pJCs) from S. japonicum induced remarkable average reductions in worm burden (54.3%), liver eggs per gram (LEPG) load (59.8%) as well as egg granulomas size (66.5%) compared to PBS control group (P【0.01), which were significantly higher than those elicited by fractions of juvenile worm cells (JCFs) or fractions of juvenile worms (JWFs) (P【0.05). Non-cell components of worms (WNCs) showed no significant protection. In trial two, compared to PBS control group, significant protective effect was also observed for cultured juvenile worm cells (cJCs) from S. japonicum with 58.4% worm reduction; 68.1% LEPG reduction (P【0.01). However, cultured adult worms cells (cACs) showed significantly higher worm burden (P【0.05); egg burden (P【0.01) when compared to cJCs. Immunological analysis of trial two revealed that cJCs engendered a Th1-biased mixed Th1/Th2 type of immune response while cACs elicited a Th2-type response. Our data indicated that immunization with both primary; cultured cells from S. japonicum juvenile worms provided high immunoprotection, for which the physical character of immunogens, stage-specific parasite; the type of immune response induced might be responsible, suggesting that vaccination with whole cells from S. japonicum larvae is a promising approach to produce protective immunity against schistosomiasis.
基金supported in part by the National Natural Science Foundation of China(Grant No.60203004).
文摘Interaction of antiworms with a worm population of e.g. hosts of worm infected and hosts of antiworm infected must be considered as a dynamic process. This study is an attempt for the first time to understand how introduction of antiworm affects the dynamic of network worm propagation. In this paper, we create a mathematical model (SIAR model) using ordinary differential equations to describe the interaction of worms and antiworms. Although idealized, the model demonstrates how the combination of a few proposed nonlinear interaction rules between antiworms and worms is able to generate a considerable variety of different kinds of responses. Taking the Blaster and Nachi worms as an example, we give a brief analysis for designing a practical antiworm system. To the best of our knowledge, there is no model for the spread of an antiworm that employs the passive scan and the finite lifetime and we believe that this is the first attempt on understanding the interaction between worms and antiworms.
