The Therac-25 and Its Accident Investigation Case Study

The Therac-25 and Its Accident Investigation - Case Study Example The Therac-25 falls into a class of machines referred to as Medical linear accelerators (linacs). They use the principal of accelerating electrons so as to create high energy beams that can be used to destroy any cancerous cells without affecting the other surrounding non- cancerous tissues. For shallow tissues, accelerated electrons were enough to treat them but for the deeper ones, the electrons beams have to be converted into X-ray photons. Defects that lead to the accidents The machine consisted of hardware and software that helped the machine run. The software also monitored the functionality status of the machine and turning on the beam. It was also responsible for turning off the beam and detecting any malfunctions. The software was responsible for running most of the machine functions in conjunction with the hardware. This therefore means that any small bug in the software will lead to malfunctioning of the machine. The software for running the Therac-25 was not extensively t ested before it was deployed for use. This was due failure to follow proper system development and implementation practices. Also the programmer didn’t provide enough documentation about the machine and software errors that could guide operators on when there is malfunction and what to do. The operators therefore were in the dark most of the time despite the machine displaying various error messages as they thought was normal. The hardware that was used to measure the dosage always provided a wrong dosage reading when it as overloaded. Instead of providing a high reading instead it displayed a low reading when it was actually so high. Another defect was how the machine was made to be operated. The machine was made that the operator and the patient were to be in separate rooms to minimize effect of radiation to the operator. Therefore in case there was any overdose and the patient complaining, the operator could not hear it. Also the operator could not ascertain whether the pa tient was in the right position every time. This was risky and costly assumptions that lead to the occurrence of the accidents. Therefore, software errors and design defects were major causes of the accidents. Collective responsibility The accidents happened over a 19-month long period and most certainly someone had to be responsible for allowing such life threatening accidents to occur for that period without doing anything. Many parties were responsible including the manufacturer, the operators and technicians and the federal government. As all the accidents happened from the first to the sixth one, the manufacturer seemed not to care. Only lame excuses were given. For example after the second accident, the manufacturer claimed it was an electrical failure even when an independent electrical firm had ruled out any possibility of the cause of the accident being an electrical fault. It was only after the sixth accident that there seemed to be any action form the manufacturer. The qu estion one would ask is why did the manufacture remain quiet for that long and let the machines to be in use when they were actually causing accidents. The federal government also had their share of the blame by allowing the AECL Company to continue with its operations despite its machines causing those fatal accidents. It was clear that the manufacturer was not following proper system development and implementation methods but yet was allowed to operate. Operators and techn

Of Mice And Men - Review Essay Example for Free

Of Mice And Men Review Essay The novel Of Mice And Men is set in the early 1930s, in the American state of California. America at this time was suffering from the effects of the depression, which followed the Wall Street Crash. This had caused many businesses to go bankrupt. Also, in this period of time America had great problems on the agricultural side of its economy. Large areas of farmland had been lashed by hurricane winds, and this had caused much of the topsoil to been blown away, leaving vast areas of land unable to grow any kind of crops. Logically this meant that less workers were needed to tend the land, so many were laid off, and as mentioned earlier many businesses had gone bankrupt following the Wall Street Crash, the combined effect of these two events led to vast numbers of people being left jobless. This gave rise to a new group of society drifters; people who would travel from place to place doing manual labour, or working in the fields. This worked to the advantage of the business owners who managed to survive the crisis, (many of these were in California, a rich state which had not been hit as badly by the depression) because it meant that there were lots of workers for few jobs. Employers could make working conditions awful, knowing that if anyone complained they could fire them and there would be five people eager to fill the place. We do not know if John Steinbecks story is based on true characters or not, but we do know that he gives a very accurate depiction of what life was like at the time, as he himself was a drifter for a period of time. One thing that becomes evident during the story is that most of the characters suffer from loneliness. One of the ways in which they coped with the loneliness was by holding onto a belief in the American dream, the dream that every man can better himself through his own efforts, and live a long and happy life. The first two characters that we meet are George and Lennie, two drifters. George comes across as the leader of the two; his job is to keep Lennie out of trouble. He shows great patience in dealing with Lennie whose mental age is the equivalent of a small child. During the book we do see George lose his temper with Lennie because it appears that he is always messing things up for George. For example when they are on their way to the new ranch Lennie produces a dead mouse from his pocket and George gets angry, You crazy fool, You gonna give me that mouse or do I have to sock you? and Blubberin like a baby? Jesus Christ! A big guy like you. George claims he only keeps Lennie around because he made a promise to his Aunt Clara that he would. Even if this is true she is now dead, and so George has no real reason to keep looking after Lennie, especially as Lennie seems to mess up everything that goes right for George. However, George still puts up with Lennie and this, it would seem, is mainly to avoid the loneliness that is caused by all the travelling. While Lennie may not be the sharpest knife in the drawer, he is still someone to converse with on long lonely walks. We learn from early on in the book that George and Lennie also share the American dream, they dream of one day having, a little house and a couple of acres an a cow and some pigs.This ambition highlights one big difference between George and Lennies grasp on reality, whilst George says he dreams of this, he must know deep down inside of him that they will never fulfil the dream. Lennie on the other hand is completely different he believes so deeply in the dream that at one point George actually threatens to not let Lennie tend the rabbits when they achieve their dream. The dream that these two share leads us to meet the next character that also suffers great loneliness. We first meet Candy when Lennie and George arrive at the ranch. He is the first person they meet. He is also the one who takes them to see the boss. Candy only has one arm and we find out later that he lost his arm in a machinery accident in the fields. However, the ranch still employs him and he was given compensation for his injury. Due to the loss of his arm he cannot work in the fields, instead he has to stay behind and sweep up. This causes him great loneliness because he has no one to talk to, his best friend is his dog, but tragically later in the story the other workers convince Candy to shoot him because he is old and useless. While the other workers can go into town at the end of the month, giving them the opportunity go out and have a good time, Candy cannot join them because he is too old to be out drinking until late in the night. His circumstances cause him to suffer from great loneliness, so it is not surprising that when he over hears Lennie and George talking about their dream, he tries to buy in to it. With the money that Candy got in compensation for his arm, it begins to look as though the dream may become a reality more quickly than George or Lennie imagined. The next character that we meet is Crooks the stable buck. He suffers from loneliness because he is black. This means he has to sleep in his own dorm and is not allowed to stay in the same dorm as the other workers. He is lonely purely because he is alone all the time and has no one to talk to. Crooks is also a cripple as a horse kicked him when he was working, leaving him with a crooked back, this prevents him from joining in many activities. He pretends, when Lennie goes into his dorm to be really angry, I aint wanted in the bunk-house, and you aint wanted in my room. But as time goes on he begins to warm to Lennie, Come on in and set a while, Long as you wont get out and leave me alone you might as well sit down. I think this is mainly because he was just glad to have someone to talk to, after being on his own for so long. Even after this though he could not resist getting revenge on the white folk, he teases Lennie asking him, Spose George dont come back no more. And he persists and begins to scare Lennie until finally Lennie gets so scared he decides to go and check if George was back yet. But Crooks quickly apologises at the thought of being left all alone again. A few minutes later Candy turns up and although Crooks acts as though he is resentful he still invites him in. The next character to appear at Crooks door is Curleys wife. She is the only woman on the ranch, and the guys refuse to talk to her because of Curley. He is very protective and jealous of her and will try and beat up anyone who he thinks might be making a move on her. When the guys in Crooks dorm seem to shut her out she begins to insult them, Standin here talking to a bunch of bindle stiffs- a nigger an a dum-dum and a lousy ol sheep. Showing a spiteful side to her character. She only married Curley to spite her mother in the first place. One night in a bar she met a man who claimed he could make her a great star actress. We are not told how the man took advantage of her. He said that he would send a letter to her, but she never received it and blamed her mother, accusing her of destroying the letter, then to spite her she ran off and married Curley. The story has a tragic ending, all the way through the story George had warned Lennie about getting to close to Curleys wife. But this turned out to be the downfall of their dream, which had seemed so much more likely since the addition of Candy to the plot. Lennie is in the barn when she appears and starts talking to him. They start sharing stories, and she asks him why he is so obsessed with rabbits. He tells her about his obsession with stroking nice things, and she allows him to stroke her hair. She starts to complain that he will, muss it up, but when she pulls away Lennies grip tightens and she begins to scream. He puts his hand over her mouth and begs her not to because George will get angry. Her body, flopped like a fish, Lennie had broken her neck. The first people to find the body were Candy and George. They new it had to be Lennie. It is at that point that the dream is thrown into real jeopardy. Candy recognising this, immediately tries to convince George that they can still achieve their hopes, You an me can get that little place, cant we, George? Cant we? But Candy already knew the answer. George knows that Lennie was such a big part of the dream, it could not continue without him, it would almost be disloyal. George knows that the other workers, especially Curley would not allow Lennie to live after this. George goes off to find the other workers. Candy is now alone with the body of Curleys wife in the barn, he blames her for destroying the dreams of three men, himself, George and Lennie. He actually begins to shout at her, You god damn tramp. spose youre glad. George follows the other workers into the barn. He acts as though it is the first time he has seen the body. The other workers assure him that they think he had nothing to do with it, and they set off in search of Lennie. The story ends with George and Carson, one of the ranch hands, standing over Lennie. George has the gun to the back off Lennies head. He and Lennie have been talking about the dream, before Lennie knows it George pulls the trigger and Lennie is dead. The last thing we see is George going to the highway with Carson, Curley and Slim. He and Slim walk away to get a drink, George knowing that its all over. The dreams that he and Candy have shared, and that have kept them going have been destroyed.

HP-48SX Scientific Expandable Calculator Essay -- Technology Calculato

HP-48SX Scientific Expandable Calculator History The HP-48SX Scientific Expandable calculator was manufactured by Hewlett Packard and the copyright is dated 1989. At the time of release, the HP-48 series was the most advanced line of scientific calculators available to those in the technical fields. I purchased the calculator in 1991 through a high school mathematics program. It has been used extensively since then for virtually every class I have taken. So far, the calculator has never malfunctioned. Material The main material of the HP-48SX is plastic. The case is hard brown plastic. The front panel is a thin metal sheet with soft plastic buttons. The screen is a large liquid crystal display. For a much more detailed description of a similar calculator, see Kim Myers' identification section for her HP-48G. Construction The internal parts of the HP-48SX consist mainly of a small CPU and its associated connections. These connections were made by soldering. The external case of the calculator was made using the technique of injection molding. The calculator was built for convenience of use. The size is perfect for the palm of the hand. Also, rubber stoppers on the bottom panel ensure the calculator does not slip on many surfaces. Design As mentioned above, the design and construction of the calculator make it convenient and easy to use. Also, the symbols used follow standard conventions which reduces the chance of confusion. The ability to produce characters of both the English and Greek alphabets gives the user the ability to write any word or equation. The keypad interface is arranged for simple use. All the buttons are labeled clearly with primary, secondary, and tertiary operations. Functions not contr... ... peers with respect to technological possessions. My HP represents my first step into high tech equipment. Lastly, my HP-48SX symbolizes success. With its assistance, I feel I can conquer any problem. Its functions gives me the capability to do so. Also, I can check my current success by accessing the grades I hold in memory. I feel that as long as I have and use my HP-48SX Scientific Expandable calculator I will never fail. I examined my calculator with a focus on academics. Many other students did not interpret their artifacts in the same terms. Alicia Moyer wrote on a turkey sandwich and the practical and recreational aspects of it. She considers her sandwich not only a meal, but also a "work of art," as well as a mental break from her schoolwork. Her artifact study is another example of one done on a utilitarian object but with a slightly different focus.

“A Soldier” by Robert Frost

Andrew Fariello Professor Didner ENC1102 MW 3:30-5:15 â€Å"A Soldier† by Robert Frost â€Å"A Soldier† by Robert Frost Robert Frost's â€Å"A Soldier† attracted my interest to some degree. As a United States military veteran of a foreign war, I significantly related to the message that Robert Frost was sending. From my own personal experiences that I have endured while fighting in Operation Iraqi Freedom conflict in Iraq, Robert Frost's words exploded imagery into my mind breaking open another dimension that typed words on a paper could not provide alone.His poem really hit home, creating a bond between the poem and myself, making â€Å"A Soldier† a wonderful poem for me to analyze. In the poem â€Å"A Soldier,† Robert Frost uses a hurled lance that will eventually rot away to symbolize a dead solider that too, will be forgotten soon. Frost is describing a soldier that has been killed by war, and has been forgotten due to the fact that the soldier is just that: a soldier, a killer that had been killed for an unimportant ugly cause. Robert Frost portrays an image that the soldier did live for a greater cause, and should be remembered for it.Robert Frost first describes a lance that has come to rest on the ground, and will soon rot away. He is that fallen lance that lies as hurled, That lies unlifted now, come dew, come rust, â€Å"He is that fallen lance that lies,† and â€Å"That lies unlifted,† tells the reader that the soldier is dead. The â€Å"fallen lance† is â€Å"He,† the soldier. â€Å"Lies unlifted† tells the reader that the soldier is dead, not uplifted as the reader would expect to have read rather than the word â€Å"unlifted. The lance, which is the soldier, will wither away just as a lance left in the ground would rust away. Then Frost tells his readers that society doesn't see the soldier's life important enough to have solved anything, and that the soldier's death didn't hav e any meaning. Before Frost tells his readers this, he first gives a hint that the soldier's death did have meaning. But still lies pointed as it ploughed the dust. If we who sight along round the world, See nothing worthy to have been its mark, It is because like men we look too near,Forgetting that as fitted to the spear, â€Å"See nothing worthy to have been its mark† symbolizes that the soldier wasn't â€Å"worthy†, or important enough to have come to lie permanently in the â€Å"dust†, or the earth. Although society couldn't see a larger picture, and no meaning behind the soldier's death, as Frost portrays as â€Å"men† who â€Å"look too near†, the soldier did, in fact, have a greater meaning to it all. Frost portrays this theory by keeping the lance, or solider â€Å"pointed as it ploughed the dust†, meaning the solider was pointed in the right direction in his life.Lastly, Frost describes the burden that is created from our weapons, but shows us that the soldier will be triumphant after his death. Our missiles always make too short an arc. They fall, they rip the grass, they intersect The curve of Earth, and striking, break their own; They make us cringe for metal-point on stone. But this we know, the obstacle that checked And tripped the body, shot the sprit on Further than target ever showed or shone. â€Å"Too short an arc†, and â€Å"they intersect†, symbolizes that our weapons are designed to come down to earth and destroy. Break their own† and â€Å"metal-point to stone† symbolizes that once the weapons do come down, they will destroy their own race and their creations. The soldier though, â€Å"tripped† and â€Å"shot the sprit on,† depicting that he is in a better place now. And the soldier is now at peace. Robert Frost used rhyme to keep the reader's interest, and implemented it very cleverly into his poem. The last word in the first line of his poem rhymes with the last word of the fourth line.And the last word of the very next line rhymes with the last word of the eighth line, which is the same interval of lines between the first and fourth lines. This pattern continues throughout the poem, and the lines that are in the middle of these intervals, also have their last words rhyming with each other. In conclusion, Robert Frost paints an image of a passed soldier that many may have been forgotten. Although only few will see the bigger picture behind the soldier's death, the soldier's sprit has moved on to a place where it can't be exposed anymore; â€Å"Further than target ever showed or shown. â€Å"

Animals’ Roles in The Wars Essay

Written by Timothy Findley in 1977, The Wars is a novel that explores the theme of young human life under the pressing concerns during the war, specifically the First World War, seeing the world of soldiers turn into a world of violence, and how these soldiers have turned into brutes themselves. The character of Robert Ross, a nineteen year-old Canadian officer and whose life is narrated mostly from the third-person point of view, is revealed as a character that has a concern for animals—thus prompting Ross to save the horses which cost him his life in the end—amidst the brutal turn of events where death was almost certain in the killing fields. The birds, coyote and rabbits also symbolize certain events in the story.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Soldiers are typically known to be highly sensitive of their surroundings when in the fields for they cannot exactly pinpoint where and when combat might ensue or from what direction the enemy might be coming from. This is perhaps one of the reasons why Ross was able to notice the chirping of the birds while he and the rest of the soldiers were out in the war. Ross was able to take notice of the fact that each time the birds stopped singing, an attack from the enemy soon takes place. Perhaps it was mere coincidence, although one can strongly tie that event with the attacks that followed thereafter as birds are familiar with their environment more than the soldiers; slight changes in their environment, especially changes which have a lot to do with probable dangers; cause the birds to fly away. Taken with the context of the encounters of Ross with the birds, it can be said that those birds served as warning signs for the young soldier. Whenever the birds stopped singing, it is almost certain that Ross is about to encounter danger along the way. â€Å"The birds, being gone, had taken some mysterious presence with them (p. 81),† showing how the sudden absence of these birds felt rather unusual, as if to signal something bad is about to happen.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   It is unusual as well for man and beast to have a close relationship, especially when the animal is known to be a hunter and can be a threat to the security of man. But more than that, any relationship between man and beast can mean simple companionship to a deep friendship. As far as Ross and the coyote are concerned, it can be said that the animal accompanied the young soldier to a certain extent in the story. â€Å"One night, Robert ran with a coyote (p. 25)† and when the men were out for a drink the coyote also â€Å"drunk at the brink (p. 27)† of the water â€Å"and suddenly sat (p. 28).† An observation of these rather unusual events would tell us that the coyote acted as if it was a member of the soldiers. This is interesting as it presents a revealing irony one can not easily notice; soldiers in the war, as Ross himself has observed, are violent men who are more like beasts who wielded weapons to kill. With the presence of the coyote among the group, it can be said that they, too, were much like the coyote. The soldiers, in fact, â€Å"gathered like whispering conspirators around the edges of a bright sheet of water (p. 27),† a sly trait typical to that of coyotes.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   While coyotes symbolize how men in the war have turned into beasts, rabbits on the other hand serve as reminders for Ross to treat animals in general with respect as if they were human beings. On one occasion, Ross was hesitant to kill the rabbits as ordered by his estranged mother, Mrs. Ross, shortly after the death of Rowena, Robert’s older sister, since they gave him memories about his older sister and since Rowena owned those rabbits. â€Å"Rabbits had to die, and Robert had to do it (p. 18),† which presents one conflict in the novel—the conflict between the command to destroy the animals which pin back memories and the apparent weakness of the main protagonist to kill even animals. It can be said that if Ross decides to kill the rabbits, it was like as if he has killed the memories of Rowena. If he decides not to kill them, it proves that he is unable to even wield a weapon against these small animals, which is of course not a good sign for someone who would enlist in the army during the war. It also shows how Ross was more human than anybody else in the story, especially his estranged mother and the rest of the soldiers in his group. His inclination to preserve whatever memory remains from the departed tells us that Ross is not keen to destroy, or that he is not a natural â€Å"destroyer† of animal life which, ironically, cost him his life as he tried to save some of the Army horses after killing two of his fellow soldiers.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   The point where Ross tries to save the Army horses was also the time when he finally turned to madness and prompted him to kill the lives of his fellowmen. Apparently, it is a contrast which tells us that insanity can push a person to kill other people yet care for beasts. That is because Ross himself has finally become a beast near the end of the story and, thus, he is now more than inclined to save his own kind rather than protect and preserve the life of other men. He is no longer the same man at the start of the story who was afraid to kill. This transformation can be attributed to the onslaught of the war, which seemed to have absorbed Robert right into it. As he was now unable to rise above the madness of the war, Robert Ross eventually turned quite like the rest of the army, willing to kill and die just so to save other lives although this time he saved the lives of horses.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   The animals in the story offer an interesting insight into some important events in the novel, especially in terms of how the life of the protagonist, Robert Ross, always hanged in the balance of making crucial decisions. In general, the story is able to reveal how the lives of soldiers always deal with certain conflicts individually and together as a group. Findley’s novel is also able to show how young minds of young individuals tend to fold under pressing moments in their lives. Reference Findley, T. (1996). The Wars. Penguin: Canada.