Art of War Studies Essay Example for Free

Art of War Studies Essay What is War? In order to describe what war is one has to define it. According to The Collins Dictionary war is 1. open armed conflict between two or more parties, nations or states 2. a particular armed conflict: the 1973 war in Middle East. 3. the techniques of armed conflict as a study, science, or profession. 4. and conflict or contest: the war against crime. 5. (modifier) of, resulting from a characteristic of war: war damage; war history. This is obviously straight to the point, but does not go into enough detail to fully describe what war is. Clausewitz chooses not to follow the definitions put forward by, what he calls, publicists, in Vom Kriege. Instead he puts forward his own view that it is nothing but a duel on an extensive scale. To fully understand what war is you have to look at the four main factors in war; force, the agents involved, intensity and duration, and teleology. The use of force and the violent nature of it is arguably the most obvious feature of war. However, one has to consider what force actually is, the answer to this creating significant disagreement. When talking about the use of force as a feature of war one immediately considers this force to be of military form, whereby weapons are used to strike down their opponents. This is of course true to an extent, but is not the only force used in war. Force can also be political or ideological force, as seen in the beginnings of the Cold War. Here, the Soviet Union uses their ideological ties with other countries in Eastern Europe to force them to reject the Marshall Plan in their war against the United States of America (US) for dominance. Clausewitz Total War, whereby the nations uses all of their wealth and resources, putting them on the line, in order to destroy their enemys armies, property and even their citizens, ties in with this use of force. Here, force is everything that the attacking group can muster together in order to destroy the other groups will to fight and bring a quick, decisive victory, and can involve killing soldiers as well as destroying important buildings. Wars are not always like this, and with the introduction of nuclear weapons, Van Creveld believes that conventional war is effectively at its end. Also, if this Total War was true then more groups would use nuclear weapons in order to win the war, but they do not. This is due to mutually assured destruction and the risk of a backlash from other nuclear powers. There has been plans to try and incorporate nuclear weapons into conventional war, but this was unsuccessful. When considering what is war, it is not simply a case of the use of force by the attacking party, but one has to take in account the opposed force. Without this opposed force it would not be war, it would simply be a massacre or perhaps genocide. The form of opposition force, like an attackers force, can vary, whether they respond in an offensive or defensive manner. If they are defending the war will be restricted to their own turf and their forces concentrated on preventing attack and protecting certain people or buildings. However, the offensive force of the attacking party can be met with similar offensive force. The war will ultimately begin on their turf as they are being attacked, but they will attempt to remove the threat and then attempt to destroy them as in Clausewitz Total War. If force is indeed the use of weapons, then one has to consider what sort of weapons are used in war. Weapons have changed through time, becoming increasingly high-tech to the point of nuclear weapons that could remove all humans off the face of the earth, but they have not been used to their full extent as of yet. The larger powers tend to use weapons such as aircrafts with bombing and firing capabilities, tanks and battleships, whilst the soldiers involved will carry such things as guns and grenades. Martin van Creveld puts forward his thesis that in future wars weapons will become less sophisticated due to the types of groups involved. With this, he believes the production of high-tech weapons will stop and cheaper, but still effective weapons, will be used. This is already happening in the war between Al-Qaeda and the West, where they are trying to bring down the US and the whole western system. They did not kill people with high-tech weapons in their most devastating strike against the US, which killed thousands of people, but took over two aeroplanes around New York and flew them into two buildings, which were among the most important in the West, showing it does not have to be all guns and bombs in wars. Another important part of war is the agents involved in it. In todays world, since the Peace of Westphalia, one would find it very tempting to say that war is a game played out by states. However, it is increasingly emerging to be not just a game played by states, but other groups are emerging that take refuge in sympathetic states that wage war on other states or groups. One such group is Al-Qaeda, which took refuge in Afghanistan in their fight against the West. If it is states fighting wars then this will be very similar to Clausewitz Trinitarian war, which is made up of a trinity of the government, the army and the people. In this situation, the government decides whether to go to war but they do not fight it. The army are strictly the players in the game and the ordinary civilians are not allowed to join in at all. If indeed this is true then all wars in the world would be an army versus an army. However, in todays world we see wars break out between armies and a group of civilians, like the situation in Iraq at the moment and the War against terror. Wars can even break out between two non-army organisations, such as a gang warfare between Mafia groups, although obviously the scale will not be as big as van Crevelds conventional war. These wars which do not occur between armies does not fit into Clausewitz Trinitarian war, but is more an element of van Crevelds non-Trinitarian war. He sees a decline of the state and with this the liquidation of boundaries between the trinity. This means that it will not only be armies that fight wars, but also groups of civilians, as seen with groups like Al-Qaeda. This arises another important part of war, which is how intense or how long it has to go on for in order for it to be classed as a war and not a skirmish of any other act of violence that is not a war as such. A war cannot simply be a single gun fight between two gangs as this is just a one off event. It has to be a series of events or battles between two or more groups for a certain cause. The saying you may have won the battle, but you have not won the war, although is a very dramatic saying, is perhaps the most obvious quote that war cannot just simply be one battle, that would be a skirmish. War is number of these skirmishes and would ultimately be more than two. The intensity is another matter, and this varies from war to war depending on the strength, nature and will to destroy of the groups involved. Wars do not necessarily have to be high intensity, although Clausewitz Total War would be, where as Van Crevelds Low Intensity Conflict would not. War would not happen if it was not fought for a certain reason, for that fact one has to understand what means war is fought for. This can be seen in Clausewitz definition that war is the continuation of politics by other means. War is not always going to be fought for political reasons and can in fact be due to such things as ideological and economic factors. In conclusion one can see that the definition of war in a dictionary is not explicit enough. Saying war is an open armed conflict between two or more parties, nations or states is much too thin an answer to discuss what war is in who is involved. Discussing fully the four factors in the introduction brings about a clear definition of war, which cannot really be put into a few sentences as it varies a great degree and is ever changing through time, whether it be who is involved, the weapons used or the means of which it is fought for. Bibliography Martin van Creveld Transformation of War Carl von Clausewitz On War Lawrence Freedman War The Collins Dictionary

Static Channel Versus Dynamic Channel Allocation Systems Computer Science Essay

Static Channel Versus Dynamic Channel Allocation Systems Computer Science Essay Abstract- Channel Allocation Schemes have always held a vital role in achieving better performance of wireless networks. This paper has studied the comparison between two of the most known techniques of channel allocation namely: Static Channel Allocation and Dynamic Channel Allocation. The comparison is made over two types of networks single radio network, in which each of wireless node is equipped with only one radio interface, and multi radio network, in which each of the node is equipped with at least two transceivers. This paper presents the detail survey of all the existing comparison made between these two schemes. Keywords- Channel Allocation Scheme, Dynamic Channel Allocation, Static Channel Allocation, Single radio network, Multi-radio network Introduction Growth in the customers of the wireless networks, let it be cellular systems or any other Wireless network, has amplified the need to have the networks which can have more capacity and accommodate more and more users. Enlargement of wireless market has made capacity of the wireless network a scarce resource. Methods to improve effective capacity utilization of the wireless network are under consideration and in [4], it is realized that these methods involve source coding schemes, power control, better modulation schemes, improved antennas. Other then these methods capacity of wireless system can be improved by installing more bas stations i.e increasing number of transmitting equipment or improving hardware equipment of current system. Using better channel allocation schemes is also one of the methods to improve capacity utilization of wireless network. The aim of this paper is to focus on channel allocation schemes. These channel allocation schemes are not much of importance in the wired networks because their topology is stable and they do not offer any mobility to the users/nodes. But in the wireless networks, channel allocation of key importance. The vital role of the wireless networks is that they offer mobility to users hence, the channel allocation algorithm has to assign channels to ports and portables so that best trade-off between the quality of service and system performance is maintained [3]. A given spectrum of frequency, can be divided into several independent sets, these independent sets are completely disjoint with each other. Hence even if they are used simultaneously, they will not interfere with each other. So splitting the frequency spectrum into independent channels and then using all the channels for communication simultaneously present improvement in the capacity utilization [6]. The channel allocation strategy is considered to be the core of mobile networks because it not only affects the quality and the availability of the channels to the user but changes the distribution of the traffic and hence, overall shapes the capacity of the network [3]. Two of the most common channel allocation schemes are considered in this paper namely, FCA- Fixed Channel Assignment or Fixed Channel Allocation and DCA- Dynamic Channel Allocation. Fixed Channel Allocation (FCA) Fixed Channel Allocation is also known as Static Channel Allocation. It is known as Fixed or Static because once the channel is allocated to a port or a user it does not change for the entire course of operation. It is used in all TDMA/FDMA digital cellular mobile networks [5] as number of frequency carriers in each cell stays fixed and does not depend on traffic load. It is a time insensitive solution, as with the passage of time allocation of the channels to nodes does not change. Although in real-time, traffic load in a cell varies, there are peak hours when the traffic load reaches to almost 100% and then there are quiet hours in a cell when traffic load is very low. This limitation dispirits the use of the FCA. But if a static condition is considered there is most likely a chance to get good performance with this channel allocation algorithm [3]. In a cellular system based on the FCA, channels are partitioned among the cells permanently so that if all the cells use all the channels assigned to them simultaneously, there will be no interference [1]. Figure cell pattern for Static Channel Allocation with N = 7 With more complex systems other channel strategies can achieve higher efficiency but they require processors with more memory. But it is an essential sacrifice to make as in [4] it is discussed that in each cell there are no static conditions, space traffic imbalance varies from 10% to 70%, and this imbalance in the traffic depends on the size of the cell or service area and type of the environment, whether its urban, suburban or rural area [4]. Dynamic Channel Allocation (DCA) In DCA, frequency channels are not fixed for any node or user. Depending upon knowledge of the environment, channels are assigned to the user. The distribution of the frequency carriers in a cell depends upon distribution of the users/nodes in the cell and also on offered traffic load. DCA is currently supported by the GSM [5]. In Dynamic Channel Allocation Scheme all the channels which are available for a system, are kept in a queue or a spool. These channels are allocated to any cell temporarily. The only constraint is to fulfil the distance criteria, so that interference can be minimized [2]. The existing schemes for the Dynamic Channel Allocation can be categorized into three main types: IA-DCA (Interference Adaptive Dynamic Channel Allocation), LA-DCA (Location Adaptive Dynamic Channel Allocation) and TA-DCA (Traffic Adaptive Dynamic Channel Allocation), these schemes are based on the type of network dynamics they consider while making decision [4]. All DCA schemes basically evaluate the cost of using each available channel and opts the channel which introduces lowest cost [2]. For most accurate and good decision for channel allocation, the algorithm should have accurate knowledge of the environment [3]. The main algorithms which are considered under the study of Dynamic Channel Allocation are: DCET, Bellcore and Segregation DCA [3]. In DCET and Bellcore DCA algorithms, the decision of channel allocation is based on only single measurement of channel dynamics, while in the Segregation DCA, a radio interface acquires the channel depending upon its learning through past experience of channel usage. With the past knowledge, channel which has highest probability of success is chosen for operation. Although this algorithm requires processors with memory yet as decision is more meaningful so its performance is better than the DCET and Bellcore DCA algorithms [3]. In figure 2, in [7] results of performance of different type of DCA schemes are compared. Figure Performance of Different DCA methods Section II of the paper compares both of the channel allocation schemes in a single radio network and Section III shares the comparison done of channel allocation schemes in multi-radio network. Section IV shares the identified regions in which future work can be done and Section V concludes the paper. Comparison of DCA and FCA in Single Radio Network A single radio network a network in which all of the nodes of the wireless network consist of maximum of one radio interface and this single radio interface is used for the communication purposes. In this section the comparison of the DCA and FCA in single radio network is presented. Figure Algorithms for Dynamic Channel Allocation In a given cell, if a node requests a call, it will be served only and only if the cell has an unused channel available, which fulfils the reuse criteria, otherwise the call will be blocked [1]. Such is the case with Static Channel Allocation Scheme. But this is not the case with the Dynamic Channel Allocation Schemes, as for each of the call that is to be served; channel is taken from the overall pool that holds all the channels available for wireless system. In any channel allocation strategy, main aim is to find the best possible way to reuse the channels to maximize the systems capacity, while keeping interference in the system at minimum and provide quality of service to the user [4]. From another view, for allocating channel, the objective is taken as to allocate the channel to a call so that number of blocked calls is minimized and the number of dropped calls is also minimized. In the end, the channel allocation scheme finds the best trade-off between these two objectives because generally priority is given to minimize the number of dropped calls, as having a call dropped is more undesirable then not having the call connected at all [1]. Both schemes for channel allocation FCA and DCA are compared under the assumption that the call arrival distribution is Poisson [5]. For the purpose of modelling in FCA it is considered that there are z numbers of channels per frequency carrier and y is the number of control channels. In a given cell i, let total number of frequency carrier be Ci and the total number of channels in the cell, which will be used to serve a call will be ci. The expression for ci is given as: (1) While this will not be the case for DCA, as frequency carriers are not permanently assigned to any of the cell. As the channel assignment depends on environment so, if we take n as the number of active calls in any cell, then frequency carriers allocated to that cell will be: (2) Total number of channels required, for any cell should be equal to the number of active calls and the control channels. But the number of frequency carriers which has z number of channels each should be either more or equal than actually required [5]. In equation (2), shows that value is always taken equal or greater than a [5]. For the first simulation, the arrival rate of the calls is set at the overload value; this means that the overload period is considered where the numbers of calls initiated per minute are more than the actual capacity of the system. The observation made over here is that, under heavy traffic load, efficiency of the network or the channel utilization and capacity of the network does not improve by using DCA instead of FCA. Although it was considered as the fact that DCA will always perform better than FCA. Figure Effect of the handover on FCA and DCA In figure 4, the phenomenon observed is known as phenomenon of low capacity island [5]. Under heavy load, no benefit is achieved by using DCA, as in such a scenario both of the schemes will be utilizing capacity to the full extent. Rather DCA may perform worse than FCA. The reason is that due to dynamic channel allocation, a cell may borrow some of the frequency channels form the neighbouring cells during the low traffic period and the neighbouring cell does not get the channel back. The cell which has obtained the channel is let us say known as the lucky cell, and the cell which donated the channel and in the end, was unable to get it back is known as unlucky cell [5]. Now during the high load traffic period, if lucky cell wants to handover the call to a neighbouring unlucky cell. But as the unlucky cell would already be out of available channels to be able to serve the call, call will be dropped. Hence under such a scenario the drop out probability of dynamic channel allocation sch eme would be higher than static channel allocation algorithm. Other simulation is to find out the effect of the arrival rate on call blocking probability. Arrival rate is the number of calls initiated per minute. Through simulation, it is concluded that DCA performed better if the traffic load is within the range 0.6 to 0.9 Erlang/BS/Channel. (figure 5) Figure Analysis of DCA and FCA, call blocking ratio with respect to the arrival rate of the calls During the next case it was considered that arrival rate is Poisson and the other parameters like handover rate and call holding time etc are evenly distributed all over the cell. From the figure 6 it is clear that as probability of call blocking increases with the increase in the arrival rate of calls. Which is fairly obvious, more are the number of the users which are to be served, there is more likely a chance that some of them may not be able to get a free channel. Figure Performance analysis of FCA and DCA, Arrival rate of calls with respect to the over all blocking probability Under such consideration as can be observed from the figure 6, DCA performs better than FCA, as in case of congestion in a cell, DCA can borrow channels from the neighbouring cells but in case of FCA, the scheme has no option but to reject the oncoming calls in case of congestion. Figure 7 shows the amount of traffic carried by FCA and DCA according to the traffic load. Figure comparison between FCA and DCA with respect to the carried traffic under the traffic load Figure 8 shows the performance of the channel allocation schemes when traffic imbalance is considered. It is observed that network capacity to carry data, in case of FCA, reduces significantly when data imbalance is considered. But in case of DCA, there is no significant degradation in networks capacity to carry the data. There is also significant increase in the number of calls blocked by FCA, because of the increase in the traffic imbalance. But as the carried capacity does not decrease much in case of the DCA, there is not much of the increment in number of the blocked calls. Figure FCA Vs. DCA, effect of the traffic imbalance on the both channel allocation techniques Comparison of DCA and FCA in Multi Radio Network A multi radio network is the type of the network where each node is equipped with at least two or more than two transceivers. Fixed Channel Allocation in Multi-radio network It is pointed out in [14], throughput and overall performance of wireless networks decreases with increased density of radios, but major reason for this problem is that these radios do not transmit the data simultaneously as the nodes are generally configured with single radios only and this factor basically limits the forwarding capacity of the network. In [15], the authors have emphasized that with the introduction of more than one NIC (Network interface cards) in wireless networks, performance of the system can be improved 6 to 7 times, instead of just doubling the performance. The same phenomenon has been confirmed in [16]. There has been much work done, in which the performance gain in wireless mesh networks with multiple interfaces is discussed as compared to single radio interface network. In [13], capacity gain between single radio, dual radio and multi-radio wireless mesh networks is compared and realistically the gain achieved by having multiple radio interfaces in the network has been discussed. Apart from that, in [17], authors have proposed that with implementation of multi-radio Diversity approximately 2.3 times performance gain is measured in the single radio network. Under the multi-radio scenario, one important factor is to consider proper channel assignment. Each of the radios should be tuned to a frequency through which the throughput of the whole network is maximized. The introduction of multiple radios is not without the trade off of increased complexity of channel assignment schemes and the traffic allocation methods [20] and apart from that, more work is done in this domain. In [10], [8], [19], the authors have proposed some approaches to get maximum possible throughput by different channel assignment algorithms. The concept of the Static Channel Allocation in this section is extended to Wireless Mesh Networks, as before the start of the operation in the wireless mesh networks the channels are properly allocated and then till the end of the operation, the channel assignment does not change. In this section, multi-radio wireless mesh network is considered and it is observed that how by having multiple radio interfaces the performance of the network improves. Figure Performance of the FCA algorithms with 3 channels Figure 9 shows the impact of the different algorithms for the channel allocation in the three channel scheme [8]. Figure performance of the FCA algorithms with 12 channels Figure 10 shows the impact of the different algorithms for the channel allocation in the twelve channel scheme [8]. Figure 11 shows that with different channel allocation algorithms, how the increment in number of interfaces per node impacts the performance of network. In all algorithms it is observed that with the increase in number of radio interfaces per node, throughput of wireless networks improves [9]. Figure FCA algorithm comparison with different number of radio interfaces per node Figure effect of increased number of interfaces per node on the over all normalized broadcast latency In figure 12, it is shown that with different channel allocation schemes for multi-interface wireless mesh network, normalized latency for broadcast decreases with the increase in number of radio interfaces per node [9]. In figure 13, it is simulated that with the increase in the number of interfaces per node, there is not an unlimited increment in capacity utilization. Multi radios are used so that in a network there could be as many concurrent transmissions as possible. But even this has a limit to it. In [10], it is shown that after achieving the maximum level of capacity utilization, even after by adding more number of radio interfaces in a network, no advantage is gained. Figure capacity degradation with increase in the number of radio interfaces per node Figure Effect of the number of channels and multiple radio interfaces on the throughput In figure 14, it is shown that as long as the number of the available channels in a cell; are more than the number of interfaces per node, with increase in number of radios per node, throughput of the network will increase [11]. Figure throughput increment of a network by increased number of the interfaces per node In figure 15, it is shown that under a proper channel assignment and routing method, with more number of interfaces per node, the throughput of the system improves considerably [12]. In [13], as shown in figure 16 and 17, performance of fixed channel allocation scheme is compared in detail with respect to single radio network and the multi-radio network. Figure overall network capacity increment with more number of radio interfaces present at each node In figure 16, it is proved that the capacity of the overall system improves with the usage of multiple radios per node. Figure capacity of each AP with multiple interfaces per node Comparison between single radio to the multiple radios In figure 17, per Access Point capacity is simulated to have comparison between multi-radio interface per node and single radio interface per node. Dynamic Channel Allocation in Multi-radio Network: There has been little work which proves the introduction of multiple interfaces while using the Dynamic Channel Allocation provides any performance up-gradation. Analytically it is assumed that, as the introduction of multi-interfaces in wireless mesh networks improves performance, similarly the performance of networks using Dynamic Channel Allocation can be improved by introducing more than one interface on a single node. Some of the analysed parameters, which show the relative improvement in performance, are listed below: Parameter I: Improvement in the throughput of the system: In a single radio cognitive network, as shown in figure 18, the node D has two data packets of equal size in its internal queue, one for node C and one for node. Nodes E and C are at the equal distance d from the node D but are tuned at different channels. In this particular case each packet will take time t to reach the destination. Even if we neglect the switching time, cognitive radio present at D will take to switch from one channel to the other channel, the time taken to completely transmit both of the packets will be t+t = 2t. Figure Single Radio Network Now even if the same network topology is considered but now consider that each of the nodes is equipped with two interfaces (figure 19). Node D will be able to transmit both of the packets simultaneously to node C and node E, considering that interface 1 is tuned to the channel on which communication with node E is possible and interface 2 is tuned to the frequency over which communication with node C is possible. In this case there will be no delay caused by the switching of the channel. Figure Multi-interface radio network Figure Effect of channel switching Conclusion: The transmission time is decreased with the factor of N, where N is the number of interface each of the node will have. Throughput is improved with the factor of N. Parameter II: Latency of the network will decrease: With the introduction of the multiple interfaces in the cognitive radio network, latency of the network will decrease. Figure Multi-hop Single interface Wireless Network Initially considering the multi-hop scenario, considering an intermediate node, it has to receive an incoming transmission on channel 1 and then it has to tune its radio to the channel 2 to be able transmit the received transmission to the destination node. Latency of such network will consist of: Transmitting time of packet over channel 1 from source node to intermediate node: t1 Transmitting time of packet over channel 2 from intermediate node to destination node: t2 Switching time required for the interface on intermediate node to switch from channel 1 to channel 2: t3 Hence the total latency of such a system will be: t1+ t2+ t3 Figure Multi-hop Multi interface Wireless Network Now comparing the previous scenario with the one in which each of the node is equipped with at least two interfaces. Now on the intermediate node interface 1 will be tuned to channel 1 and interface 2 will be tuned to channel 2. If there is an incoming transmission on channel 1 and it is to be transmitted to the channel 2, the total latency will be: Transmitting time of packet over channel 1 from source node to intermediate node: t1 Transmitting time of packet over channel 2 from intermediate node to destination node: t2 Hence the total latency of such a system will be: t1+ t2 The switching time will not be considered over here; hence comparatively the latency is decreased with the introduction of another interface on the cognitive radio node. Conclusion: The latency factor is dependent on switching time of the cognitive radio. This factor comes into effect with more dominance with increase in the number of hops in the multi-hop network. Latency can be greatly reduced with the introduction of multi interfaces on the cognitive radio network. Parameter III: Connectivity of the network will improve: The probability of isolation of any node in a network will be reduced with the introduction of the multi-interfaces in the cognitive radio network. Figure Single interface node with the available channels Considering the scenario, in figure 23, where a secondary network has four channels available for its utilization, now for a given condition, all radio interfaces are tuned to either one of the channel 1, 2 or 3. If a single interface chooses channel 4, it will be isolated from the rest of the network. Assuming that the probability of opting for such a channel is p then the overall probability of getting a node isolated from the rest of the network will be p. Figure Multi-Interface node with the available channels Now for multiple interfaces, a node will only be separated if both the interfaces of a single node choose channel 4. A node will be isolated if and only if: Interface 1 chooses channel 4 AND interface 2 chooses channel 4 P2 As according to the probability rules p Conclusion: The probability of isolating a node, is decreased with the factor of N [N is the number of radios] as compared to the probability of node isolation in case of single interface cognitive radio networks. Here mutual independence among the DCA algorithms running on both of the radio interfaces is considered, but this is not generally the case. The performance of a cognitive radio network is strictly dependent on the number of cognitive radios present in its vicinity [21]. Figure Improvement in throughput using multiple radios Figure Improvement in throughput of the network with multiple radio using different number of available channels Figure 25 and 26 shows the throughput improvement gained by the introduction of multiple radios as compared to a single radio and in both of the figures different number of available channels are considered [24]. Comparison: Up till so far, none of the research has been carried out to find out whether any advantage is gained by deploying Dynamic Channel Allocation scheme in the multi-radio wireless network domain as compared to the implementation of the Fixed Channel Assignment algorithm. Considering the study made regarding the performance improvement gained by fixed channel allocation scheme and dynamic channel allocation scheme in multi-radio wireless network, there could be several hypotheses made. The complexity of implementation of Dynamic Channel Allocation algorithm will be more than that of Fixed Channel Allocation algorithm. Although the same is true in case of single radio network, but in case of the Multi-radio network, the complexity increment will be more significant. The reason can be taken as if the spectrum view of a single interface of a node changes in multi-radio network, for the similar node the situation changes for the other interfaces as well [21]. The performance improvement obtained by implementation of the Dynamic Channel Allocation algorithm as compared to the Fixed Channel Allocation in the multi-radio will have similar effects as it has in the Single radio network. The same effect on the throughput of the system, data carrying capacity and the effect of the traffic load and traffic imbalance will be observed. Another important factor that can be predicted because of the observation made via simulation figures is as the performance of the wireless network depends upon the density of the nodes in a network. As compared to the Fixed Channel Allocation Scheme, Dynamic Channel Allocation Algorithms will be more sensitive to the density of the network [23]. There will be no matter of connectivity in case the Fixed Channel Assignment Scheme is deployed on the wireless network. As before the point of operation with FCA, it is made sure that all of the nodes are connected and none of the node is left isolated. With the Dynamic Channel Allocation there will still be a small probability that a node can get isolated from the rest of the network. In the Fixed Channel Allocation for the multi-radio wireless network the distribution of radio interfaces do not matter for the performance. But in case of the DCA, better performance can be improved if radio interface distribution on the nodes is not uniform. DCA will perform better if the first hop nodes have more number of radio interfaces than rest of the network nodes [22]. Future Work The points raised, during this study are just concluded through observation and analytically studying the response of the Fixed Channel Allocation Algorithm in the Multi-Radio network and Dynamic Channel Allocation Algorithm in Multi-Radio Network. These observations can be further improved by using proper simulating tools. Conclusion In the single radio wireless network, DCA exhibits better performance than FCA. The same behaviour is predicted for the multi-radio wireless network, but with the increased complexity. And much better performance can be achieved by taking care of the distribution of the radios in the network. Still it should be considered that there will not be infinite performance gain obtained by using multi-radio network and DCA. The limitation imposed is that number of channels available to a cell should always be greater than the number of interfaces per node has.

The Disputed Reign of Dowager Empress Tz’u-hsi Essay -- Essays Papers

The Disputed Reign of Dowager Empress Tz’u-hsi Historical record is not always an accurate representation of fact. An example of this would be the long reign of the Dowager Empress Tz’u-hsi, in which there were hundreds of documents written about her life. These documents have been taken and used in the production of numerous books, especially among Western historians. It was these early historians who have established the widely accepted perspective that Tz’u-hsi hungered for power, abused it, and retained it using any means necessary. This understanding is echoed today by authors such as W.G. Sebald, author of The Rings of Saturn. There are many differences between the accounts of the Western perspective and that of Sebald’s, but the overall idea of Tz’u-Hsi as a conniving and unworthy Empress is intact between the two. Still, the investigation is not over. There happens to be an abundance of historical documentation and opinion that contradicts the Western view on Tz’u-hsi. First, We stern accounts of the major issues in Tz’u-hsi’s reign will be examined; following this will be a look at how unreliable these sources are by showing their inconsistencies, where the arguments came from, and the all the other evidence supporting a different perspective on the great Empress. It is possible the Empress was everything that her enemies said she was, but the evidence at hand does not support image of a sinister Tz’u-hsi. The Western perspective on the Dowager Empress is harsh and W.G. Sebald is perhaps the harshest of all of the Western historians. One of Sebald’s first descriptions of the Empress is that her â€Å"craving for power was insatiable† (Sebald 147). Sebald wastes no time in backing up this claim. At the cru... ...istorians like Sebald recognize the uncertainty. Works Cited Bland, J. O. P., and E. Backhouse. China Under the Empress Dowager. Boston: Houghton Mifflin, 1914. Chung, Sue Fawn. â€Å"The Much Maligned Empress Dowager : A Revisionist Study of the Empress Dowager Tz’u-his.† Modern Asian Studies. 13 vol. Cambrige UP, 1979. JSTOR. 1 May 2005 < http://links.jstor.org/sici?sici=0026-749X%281979%2913%3A2%3C177%3ATMMEDA%3E2.0.CO%3B2-U>. Collis, Maurice. The Motherly and Auspicious. New York: G.P. Putnam’s, 1944. Laidler, Keith. The Last Empress. Chichester: John Wiley, 2003. Seagrave, Sterling. Dragon Lady. New York: Alfred A. Knopf, 1992. Sebald, W. G. The Rings of Saturn. Trans. Michael Hulse. London: Harvill, 1995. Vare, Daniele. The Last Empress. Garden City: Doubleday, Doran, 1938. Warner, Marina. The Dragon Empress. New York: Macmillan, 1972.

Does Human Cloning Produce An Embryo? :: Argumentative Persuasive Topics

Does Human Cloning Produce An Embryo? In February 1997, Dr. Ian Wilmut and his team startled the scientific world by showing that the nucleus from an adult sheep's body cell could be used to produce a developing embryo that would grow into another, genetically identical sheep. There was no doubt whatever that this process ("somatic cell nuclear transfer") produces an embryo of the relevant species. As Dr. Wilmut said in his groundbreaking article: "The majority of reconstructed embryos were cultured in ligated oviducts of sheep... Most embryos that developed to morula or blastocyst after 6 days of culture were transferred to recipients and allowed to develop to term," etc. [I. Wilmut et al., "Viable offspring derived from fetal and adult mammalian cells," 385 Nature 810-813 (Feb. 27, 1997)] Now that the discussion has turned to humans, political spokespersons for the biotechnology and pharmaceutical industries have decided to engage in a curious avoidance of the fact that somatic cell nuclear transfer using a human nucleus would produce a human embryo. There seem to be two reasons for this: a. some spokespersons maintain -- contrary to scientific evidence, the findings of the NIH Human Embryo Research Panel, and current federal law on embryo research -- that no human embryos should be called "embryos" for the first two weeks of existence.1 b. because cloned embryos are seen as such useful research material for destructive experiments, current restrictions on embryo research etc. must be evaded by denying that an embryo produced by cloning deserves the name. Thus euphemisms and misleading or inaccurate terms ("totipotent cell," "clump of embryonic cells," "unfertilized oocyte," etc.) have entered the political discussion. They are employed to conceal the fact that researchers want to be allowed to use cloning to produce and destroy human embryos. Biotechnology groups claim to oppose the cloning of "human beings" or "persons" -- but they reserve the right to conduct cloning experiments on human embryos and fetuses, so long as none is allowed to survive to live birth. Fortunately, one can cut through the political evasions by looking at the professional literature -- including writings by those who support cloning of embryos for research purposes: "One potential use for this technique would be to take cells -- skin cells, for example -- from a human patient who had a genetic disease... You take these and get them back to the beginning of their life by nuclear transfer into an oocyte to produce a new embryo.

Vincent Van Gogh :: essays research papers

On March 30, 1853 Vincent Van Gogh was born in the small village of Groot-Zundert, Holland. When he is eleven, he begins schooling where he starts to draw for the first time. People begin to notice how magnificent his works were, and after he finishes school he begins to sell his paintings to art dealers. Van Gogh starts spending more time with his brother Theo. They create a deep bond with each other and discuss things, which today, help us understand Van Gogh much better. In 1873, he joins the London branch of the art dealers he originally started out with. He spends most of his time in museums and learns a great deal of information. He likes living in London and soon falls in love with the daughter of the owner at the boarding house where he was living at the time. He gets rejected which puts him in a deep depression, which distracts him from his work. He is soon transferred to the Paris branch of the art dealer. There is not much for him Paris so within a year he returns to L ondon. Even though he is back in London, he is still very distracted in his work. At the same time, he becomes obsessed with bible studies. Van Gogh resigns from his position in 1876 and leaves for Ramsgate, England. There, he takes a job as a teacher and curates with the local minister. The more obsessive his interest in religion gets, the worse his physical and mental state get. He leaves England a year later to take up religious studies in Amsterdam. He soon comes to an end of his formal religious studies, and travels to a small coal-mining district in Belgium. Conditions for the miners are terrible, but Van Gogh reads them the bible and gives them hope. Soon enough, he devotes all of his time to helping the miners by bringing food and clothing to the miners. Although his superiors like what he is doing, they believe that his behavior and religious belief is extreme. His position in the mining district is discontinued and he suffers great depression. In 1880 comes the turning poi nt of Van Gogh’s Life. He once again becomes interested in art and takes up further education at the academy of Brussels. He spends time with another painter Anton Mauve who introduces him to water colors.

The Cash Flow Statement

The Cash Flow Statement * A Cash flow statement is a financial report that shows the sources of a firm’s cash and its uses of cash. In other words, it answers the questions, â€Å"where did the cash come from? † and â€Å"where did the cash go? † Measuring Firm’s Cash Flow You can explain the cash inflows and outflows of a business by looking at three cash flow activities. * Cash flow activities: 1.Generating cash flows from day-to-day business operations It is the informative to know how much cash is being generated in the normal course of operating a business on a daily basis, beginning with purchasing inventory on credit, selling on credit, paying for the inventory, and finally collecting on the sales made on credit. 2. Buying or selling fixed assets. When a company buys (or sell) fixed assets, such as equipment and buildings, cash outflows (or inflow) result. These cash flows are not part of the regular day-to-day operations and, consequently, are not included in the income statement.They appear only as changes from one balance sheet to the next. 3. Financing the business. Cash inflows and outflows occur when the company borrows or repays debt; when it distributes money to the owners, such as when dividends are paid; or when the owners put money into the business in the form of additional equity. Profits versus cash flows * Entrepreneurs need to be aware that profits shown on a company’s income statement are not the same as its cash flows. * An income statement is not a measure of cash flows because it is calculated on an accrual basis rather than a cash basis.This is an important point to understand in section. * In Accrual-basis accounting, profits are recorded when earned- whether or not the profits have been received in cash- and expenses are recorded when they are incurred- even if money has not actually been paid out. * In Cash-basis accounting, profits are reported when cash is received and expenses are recorded whe n they are paid. * There are several reasons, including the following, that profits based on an accrual accounting system will differ from the firm’s cash flows; 1. Sales reported on an income statement include both cash sales and credits sales.So the total sales do not correspond to the actual cash collected. 2. Cash spent for inventory doesn’t represent all inventory purchases since some inventory is financed by credit. 3. The depreciation expense shown in the income statement is a noncash expense. It reflects the costs associated with using an asset that benefits the firm’s operations over a period of several years, such as a piece of equipment used over five years. What every small business owner should ask and understand is, â€Å"How do you compute your firm’s cash flow? †

My Country

Our Country Our Country, the Union of Myanmar, is known as the land of golden pagodas. Myanmar is surrounded by big countries like China in the north and India and Bengladish to the west. Thailand and laos lie to the east of Myanmar and the south is the east of Myanmar and the south is the sea. Its area is about 676553 square kilometers, and it is the second largest country in Southeast Asia after Indonesia. Although it is still a developing country, we can say it has good neighbours, great resources and beautiful natural surroundings. And, Myanmar is divided into seven states and seven divisions. There are althogether 135 ethnic groups, like Kachin, Kayar, Kayin, Chin, Bamar, Mon, Rakhine, Shan, Palaung, Paoh and different races like Chinese and Indians, living in unity. Our country is situated near the Bay of Bengal, it has monsoon climate. It is colder in the north than in the south, and the central region is dry. It has three separated seasons, the hot season, the rainy season and the cold season (winter). Each season lasts about four months. The hot season begins in February and ends in May. The rainy season is from June to September. The cold season starts in October and ends is January. The hot season is the most unfavourable season in our country as it is the most unpleasant time to live. It is really hot, dry and dusty. The lakes and wells dry up in this season. Leaves fall from trees, making some trees bare with dry branches till the middle of the season. New buds come out after that and make them look pleasant thought. People have to cool themselves in various ways using fans, air-cons, and travelling and staying in summer resorts like Pyin Oo Lwin and Kalaw. In spite of the annoying heat, there are festivals like Water Festival, Kason water Sprinkling Festival and Pagoda Festival, which can release the people from the extreme weather. The Thingyan is one of the most enjoyable festivals in this season. After the hot season, it is the rainy season. In this season, it is very wet and some places are very muddy. The trees and leaves turn very green as their original colour returns when the dust is removed. Sometimes, it is very frightening because of the thunder, lightning, storms and floods. But, farmers expect the rain to start growing paddy, and rainwater is essential for everyone to live. The next season to come is the cold season. It is quite pleasant and cold in most parts of our country. Flowers bloom beautifully under the mist and fruits and vegetables are abundant in this season. People take exercise and walk in the early morning to get fresh air. Sporting events like marathon, running and walking races are held throughout the world. Religious Lighting Festival, Tazaungdine also falls in this season and it is very delightful to see the surroundings with colourful lights. After enjoying the Christmas festival and hailing the new year, our Independence Day tournaments which are also full of fun and merry-making arrive on the fourth of January. It is the best time of the year in our country as the weather is neither hot nor wet. Our country has four important rivers, called the Ayeyarwady, the Chinwin, the Thanlwin and the Sittaung. They are a great help in transportation and make it possible to grow different kinds of crops. As our country is an agricultural country, we grow rice, and crops the whole year round, and export rice, beam, prawns and fishes. It is also full of mineral resources like Jade, sapphire, ruby, gold, silver and various kinds of metal. Myanmar pearl is also world famous for its quality. In the forests, we have abundant supply of teak, ironwood and other kinds of hard wood. Myanmar woven clothes and handicrafts like tapestries, lacquerwares, sculptures of various kinds of wood and other wares also reflect the culture of Myanmar people. The national museum, Planetarium Yangon Zoological graden, Hlawga Wildlife park, Aquarium lakes, amusement parks, natural caves, waterfalls, bird sanctuaries, mountain resorts, summer resorts, various creeks and rivers and botanical gardens are the countless attraction of Myanmar, our country. However, as it was once a colony of the British and the Japanese the people were influenced by different missions of different religions So, there are some Christians, Hindus and Muslims. But, our country have independent since 1954. So, the other religions live together peacefully under the teachings f different religions So, one can see various sizes, styles and shapes of pagodas, images, monasteries, churches, temples and mosques everywhere in our country, Myanmar. The capital of our country is Yangon and, Mandalay is the second largest city and the last capital of Myanmar kings. Naypyitaw is also the large and important city for our country. Bagan is the most famous places with thousands of pagodas. It is very attractive for all people because we can see most of the religious relics and buildings. It is also attractive for foreigners because it has ancient culture, arts and crafts. Bagan is situated on the east bank of the Ayeyarwady in central Myanmar. It is about 5 kilometers south of Nyaung Oo. Its area is about 16 square miles and it has a hot and dry climate. It was the capital of the Myanmar kingdom during the Bagan dynasty which was from 11th to 13th centuries. It became the centre of Buddhism after King Anawrahta attacked Thaton in 1057 and brought to Bagan the Buddhist monk, Shin Arahan, the sacred Pitakas and the sacred Pali language. Bagan has always been famous for its ancient pagodas and monuments and is recognized by the world’s travellers as one of the world’s wonders. The architecture and the artistry of the craftsmen show Myanmar’s wounderful achievement in arts and crafts. The lacquareware of Bagan is still very much in use, and stands as a traditional attraction for all of us. There are also places of interest like the Bagan Archaeological Museum, the Myanmar handicraft shops and many other antique shops. Today, Bagan has become a tourist attraction because of its archeological sites and unspoilt beauty. It is such as attractive place for both natives and foreigners. The Shwedagon Pagoda is the most ancient historical pagoda in Myanmar. The history of the Shwedagon says that the Gotama Buddha gave eight hair relics to the two brothers, Taphussa and Ballika, who went to India as traders. They brought the relics to their hometown, Okkalapa, now known as Yangon. They gave the sacred relics to the king of Okkalapa. The king and the citizen built the first pagoda in Myanmar. This pagoda, known as the Shwedagon, enshrines not only the eight hair relics of Gotama Buddha but also the relics of Kakusam Buddha, Konagan Buddha and Kassapa Buddha. So, it is regarded as the most sacred pagoda. This pagoda was rebuilt and enlarged by later kings. The last person to rebuilt the pagoda to the present size and shape was Queen Shin Saw Pu. The pagoda is 326 feet tall and its circumference at the base is 1420 feet. Its festival is celebrated every year in the last month of the Myanmar calendar called Tabaung. It is celebrated for seven days culminating on the full-moon day of Tabaung. The Pagoda is covered with gold from top to bottom. It glitters in the sun-light like solid gold. It is well known not only in Myanmar but also in the whole world and many pilgrims from all over Myanmar as well as from abroad have visited the Shwedagon. There are also many other places of interest in Myanmar, our country. Inlay is one of the most beautiful places in Myanmar. Most of the people who live there are Shans, Pa-ohs, and Danus. They are hospitable and honest. Inlay is a big lake with floating islands. Various kinds of vegetables are grown there. Vegetables are fresh, cheap and plentiful. People in Inlay have a market day every five days. It is very crowded with people selling and buying all kinds of goods, in moving boats. Their lives in boats are very interesting. There are only two places in the world where people row the boats with their legs. One is in Venice, Italy and the other is in Inlay. That is why Inlay is known as Venice of the east. As it is in Shan State, the weather is cool and pleasant. We can also enjoy ourselves by taking a motor boat ride on the lake. It is very exciting to feed the sea-gulls from a moving boat because they sometimes bite our fingers. The famous Phaung Daw Oo Pagoda is in Inlay so we can go on a pilgrimage there. Its festival is held in October and people from all over the country go there to pay homage to the images of Buddha. There are many beautiful and pleasant places which are worth visiting and seeing in Myanmar. Pyin Oo Lwin is a hill station. It is 42 miles from Mandalays. The sight of the blue mountains and green valleys along the way is pleasant. It is a quiet town with beautiful gardens. The streets are clean and less crowded and there is hardly any noisy traffic except in the town centre. The atmosphere is peaceful and the climate is pleasant. It is refreshing to go for a walk in the early morning. It is cold during the winter months and cool in summer months. In the evening, the breeze often brings its sweet smell, and the air is clean. Fruits and vegetables are cheap and plentiful the whole year round. The main attraction of Pyin Oo Lwin is the famous National Kandawgyi Garden. There, we can see real natural beauty and different varieties of the most beautiful and colourful flowers in Myanmar. The Pwe Kauk water fall is the place where families have their meals enjoying the beautiful views. We can go on to visit the Maha Arnthtoo Kantha Pagoda and pay homage to the Buddha image. Many visitors take photographs at the Peit Chin Hmyaung Cave which is the pride and wonder of the town, Pyin Oo Lwin. The cool breeze and the beautiful landscape attract many holiday – makers. Natural beaches like Ngapali, Ngwe Saung, Kan Thar Yar, Chaung Thar and Maungmakan are also natural unspoilt places where we can get perfect peace and relax ourselves. Myanmars are carefree and fun-loving people. So, there are many festivals in our country for the whole year round. Among them, the Thingyan Festival is the most famous and the year’s greatest event. It is also the most enjoyable festival in our country. The Thingyan marks the end of the old year and welcomes a new one. It usually last for three or four days. During the festival, people throw water on one another. It means washing away the impurities of the old year. People of different ages, young and old, take part in it. People set up pandals or stages and throw water and revellers who go round the city in open cars. Most of the revellers are teenagers and children get lots of fun, playing in the wet. Water-throwing, shouting and teasing are accepted as a natural process during Thingyan. People get into a forgiving mood and even mere strangers treat each other as long-lost brothers. No one seems to be angry for being wet. We can watch many stage shows and dance shows everywhere. It is not only a time for doing good things. Old people go to pagodas and monasteries to meditate or keep Sabbath. Young people wash the hair of the elders and cut their nails. Most people avoid doing bad things during this period. The whole country is alive with fun and activities. Thingyan is the festival in which we can get the greatest fun for the longest period. The Myanmar people are kind, hospital and generous. They are also simple, honest, helpful and friendly. In fact, they are peace-loving people. It has an international air-port and a beautiful port for ocean lines. It is also the gateway into Myanmar. We can be proud of our tradition and culture, and Myanmar is self sufficient. It also produces building materials such as wood and bamboo. There are also many scenic places and pleasant beaches which are very attractive for tourists. People in our country love, regarded by foreigners as helpful, smiling and even easy-going people mistakenly. In fact, Myanmar people are simple and loving. They are also hardworking. Although Myanmar is a developing country, there are a lot of natural resources that we haven’t explored and places of interest to be renovated and attract the tourists. With the improvement of modern technology, we will be able to discover all these and apply for the all-round development of our country, Myanmar. Presented by, 2 GC – 19 Ma Hnin Ei Khaing TU (HINTHATA)