Ind.chapter 2
Prentice Hall's Federal Taxation 2013 Individuals, 26e (Pope)
Chapter I2 Determination of Tax
1) Gross income is income from whatever source derived less exclusions.
Answer: TRUE
Page Ref.: I:2-3
Objective: 1
2) Although exclusions are usually not reported on an individual's income tax return, interest income on state and local government bonds must be reported on the tax return.
Answer: TRUE
Explanation: See Additional Comment, p. I2-3.
Page Ref.: I:2-3
Objective: 1
3) Generally, deductions for (not from) adjusted gross income are personal expenses specifically allowed by tax law.
Answer: FALSE
Explanation: Personal expenses, if deductible, are generally from AGI deductions.
Page Ref.: I:2-4
Objective: 1
4) Generally, itemized deductions are personal expenses specifically allowed by the tax law.
Answer: TRUE
Page Ref.: I:2-4
Objective: 1
5) Taxpayers have the choice of claiming either the personal and dependency exemption or the standard deduction.
Answer: FALSE
Explanation: Taxpayers claim the greater of itemized deductions or the standard deduction. In addition, taxpayers will reduce taxable income by personal and dependency exemptions.
Page Ref.: I:2-5
Objective: 1
6) Refundable tax credits are allowed to reduce or totally eliminate a taxpayer's tax liability but may not reduce the liability below zero.
Answer: FALSE
Explanation: Refundable tax credits may reduce the tax liability to zero and, if some credit still remains, are refundable or paid by the government to the taxpayer.
Page Ref.: I:2-6
Objective: 1
7) Nonrefundable tax credits are allowed to reduce or totally eliminate a taxpayer's tax liability but may not reduce the liability below zero.
Answer: TRUE
Page Ref.: I:2-6
Objective: 1
8) The standard deduction is the maximum amount of itemized deductions which may be claimed by a taxpayer, and is based on an individual's filing status, age, and vision.
Answer: FALSE
Explanation: The standard deduction, set by Congress, is not directly related to itemized deductions. It is the alternative to itemized deductions.
Page Ref.: I:2-10
Objective: 2
9) Nonresident aliens are allowed a full standard deduction.
Answer: FALSE
Explanation: The standard deduction is not available to nonresident aliens.
Page Ref.: I:2-12
Objective: 2
10) The standard deduction may not be claimed by one married taxpayer filing a separate return if the other spouse itemizes deductions.
Answer: TRUE
Page Ref.: I:2-12
Objective: 2
11) An individual who is claimed as a dependent by another person is not entitled to a personal exemption on his or her own return.
Answer: TRUE
Page Ref.: I:2-12
Objective: 2
12) A qualifying child of the taxpayer must meet the gross income test.
Answer: FALSE
Page Ref.: I:2-13 and I:2-14
Objective: 2
13) For purposes of the dependency exemption, a qualifying child must be under age 19, a full-time student under age 24, or a permanently and totally disabled child.
Answer: TRUE
Page Ref.: I:2-14
Objective: 2
14) For purposes of the dependency exemption, a qualifying child may not provide more than one-half of his or her own support during the year.
Answer: TRUE
Page Ref.: I:2-14
Objective: 2
15) An individual may not qualify for the dependency exemption as a qualifying child but may still qualify as a dependent.
Answer: TRUE
Page Ref.: I:2-14
Objective: 2
16) One requirement for claiming a dependent other than a qualifying child is that the taxpayer provides more than 50 percent of the dependent's support (assuming it is not a multiple support agreement situation).
Answer: TRUE
Page Ref.: I:2-15
Objective: 2
17) When two or more people qualify to claim the same person as a dependent, a taxpayer who is entitled to the exemption through the qualified child rules has priority over a taxpayer who meets the requirements for other relatives.
Answer: TRUE
Page Ref.: I:2-16
Objective: 2
18) The person claiming a dependency exemption under a multiple support declaration must provide more than 25% of the dependent's support.
Answer: FALSE
Explanation: The minimum support percentage for a person claiming the dependency exemption under the multiple support agreement is 10%.
Page Ref.: I:2-15
Objective: 2
19) Generally, in the case of a divorced couple, the parent who has physical custody of a child for the greater part of the year is entitled to the dependency exemption.
Answer: TRUE
Page Ref.: I:2-16
Objective: 2
20) A child credit is a partially refundable credit.
Answer: TRUE
Page Ref.: I:2-20
Objective: 2
21) A married couple need not live together to file a joint return.
Answer: TRUE
Page Ref.: I:2-21
Objective: 3
22) A widow or widower may file a joint tax return and claim an exemption for the deceased spouse in the year of the spouse's death as long as the surviving spouse does not remarry before the end of the year. Answer: TRUE
Explanation: A joint return may be filed in the year of death with the deceased spouse getting a full personal exemption.
Page Ref.: I:2-22
Objective: 3
23) An unmarried taxpayer may file as head of household if he maintains a home for his qualifying child. Answer: TRUE
Page Ref.: I:2-23
Objective: 3
24) For 2012, unearned income in excess of $1900 of a child under age 18 is generally taxed at the parents' rate.
Answer: TRUE
Page Ref.: I:2-25
Objective: 3
25) Kelly is age 23 and a full-time student with unearned income of $2,000 in the current year. The total cost of her support for the year is $19,000. She is not subject to the kiddie tax.
Answer: FALSE
Explanation: She meets the age and student status to be subject to kiddie tax, and her unearned income exceeds the $1,900 threshold.
Page Ref.: I:2-25
Objective: 3
26) If a 13-year-old has earned income of $500 and unearned income of $1,500, all of the income can be reported on the parent's return.
Answer: FALSE
Explanation: To be eligible, the child's income must come solely from interest and dividends.
Page Ref.: I:2-26
Objective: 3
27) Suri, age 8, is a dependent of her parents and has unearned income of $6,000. She must file her own tax return.
Answer: FALSE
Explanation: A dependent earning solely unearned income not exceeding $9,500 may report unearned income on the parents' return.
Page Ref.: I:2-26
Objective: 3
28) Generally, when a married couple files a joint return, each spouse is liable for one-half of the entire tax and any penalties incurred.
Answer: FALSE
Explanation: Joint liability applies for the full tax.
Page Ref.: I:2-32
Objective: 3
29) The only business entity that pays income taxes is the C corporation.
Answer: TRUE
Explanation: S corporations and partnerships are both flow-through entities.
Page Ref.: I:2-27 through I:2-29
Objective: 4
30) A $10,000 gain earned on stock held 13 months is taxed in a more favorable manner than a $10,000 gain earned on stock held 11 months.
Answer: TRUE
Explanation: Lower tax rates apply to long-term capital gains.
Page Ref.: I:2-30
Objective: 5
31) A taxpayer is able to change his filing status from married filing jointly to married filing separately by filing amended return.
Answer: FALSE
Explanation: Taxpayers are not able to change their status from filing a joint return to separate returns although they can change their status from separate returns to a joint return by filing an amended return. Page Ref.: I:2-33
Objective: 6
32) Tax returns from individual and corporate taxpayers are due on the 15th day of the third month following the close of the tax year.
Answer: FALSE
Explanation: Individual returns are due on the 15th day of the fourth month following the close of the tax year.
Page Ref.: I:2-34
Objective: 7
33) Taxable income for an individual is defined as
A) AGI reduced by itemized deductions.
B) AGI reduced by personal and dependency exemptions.
C) total income reduced by the standard deduction.
D) AGI reduced by deductions from AGI and personal and dependency exemptions.
Answer: D
Page Ref.: I:2-2; Table I:2-1
Objective: 1
34) All of the following items are generally excluded from income except
A) child support payments.
B) interest on corporate bonds.
C) interest on state and local government bonds.
D) life insurance proceeds paid by reason of death.
Answer: B
Explanation: B) Interest on corporate bonds is taxable.
Page Ref.: I:2-3; Table I:2-2
Objective: 1
35) All of the following items are included in gross income except
A) alimony received.
B) rent income.
C) interest earned on a bank account.
D) child support payments received.
Answer: D
Explanation: D) Child support is not taxable.
Page Ref.: I:2-3 and I:2-4, Table I:2-3
Objective: 1
36) All of the following items are deductions for adjusted gross income except
A) alimony paid.
B) trade or business expenses.
C) rent and royalty expenses.
D) state and local income taxes.
Answer: D
Explanation: D) State and local income taxes are itemized deductions.
Page Ref.: I:2-4; Table I:2-4
Objective: 1
37) All of the following items are deductions for (not from) adjusted gross income except
A) moving expenses.
B) unreimbursed employee business expenses.
C) qualifying contributions to individual retirement accounts.
D) one-half of self-employment taxes paid.
Answer: B
Explanation: B) Unreimbursed employee business expenses are miscellaneous itemized deductions. Page Ref.: I:2-4; Table I:2-4
Objective: 1
38) Which of the following credits is considered a refundable credit?
A) child and dependent care credit
B) earned income credit
C) adoption expense credit
D) lifetime learning credit
Answer: B
Explanation: B) The earned income credit is a refundable credit.
Page Ref.: I:2-6; Table I:2-5
Objective: 1
39) A single taxpayer provided the following information for 2012:
What is taxable income?
A) $57,250
B) $63,200
C) $67,000
D) $67,200
Answer: B
Explanation: B) ($63,200 = $80,000 - $13,000 itemized deductions - $3,800 personal exemption)
Page Ref.: I:2-6; Example I:2-1
Objective: 1
40) Which of the following types of itemized deductions are included in the category of miscellaneous expenses that are deductible only if the aggregate amount of such expenses exceeds 2% of the taxpayer's adjusted gross income?
A) unreimbursed employee business expenses
B) charitable contributions
C) medical expenses
D) home mortgage interest expense
Answer: A
Page Ref.: I:2-7; Table I:2-6
Objective: 2
41) In 2012 the standard deduction for a married taxpayer filing a joint return and who is 67 years old with a spouse who is 65 years old is
A) $11,900.
B) $13,050.
C) $14,200.
D) $14,800.
Answer: C
Explanation: C) ($14,200 = $11,900 + $1,150 +$1,150)
Page Ref.: I:2-10 and I:2-11
Objective: 2
42) In 2012 Brett and Lashana (both 50 years old) file a joint tax return claiming as a dependent their son who is blind. Their standard deduction is
A) $11,900.
B) $13,050.
C) $13,350.
D) $13,900.
Answer: A
Explanation: A) Blindness of a dependent does not increase the standard deduction of the taxpayers Page Ref.: I:2-10 and I:2-11
Objective: 2
43) Annisa, who is 28 and single, has adjusted gross income of $55,000 and itemized deductions of $5,000. In 2012, Annisa will have taxable income of
A) $45,250.
B) $49,050.
C) $50,000.
D) $46,200.
Answer: A
Page Ref.: I:2-11; Example I:2-4
Objective: 2
44) On June 1, 2012, Ellen turned 65. Ellen has been a widow for five years and has no dependents. Her standard deduction is
A) $3,800.
B) $5,950.
C) $7,400.
D) $11,900.
Answer: C
Explanation: C) $5,950 + $1,450 = $7,250
Page Ref.: I:2-10 and I:2-11
Objective: 2
45) The regular standard deduction is available to which one of the following taxpayers?
A) married taxpayer filing a separate return where the other spouse itemizes
B) a person who has only unearned income and is a dependent of another
C) an individual filing a return for a period of less than 12 months because of a change in accounting period
D) an abandoned spouse
Answer: D
Explanation: D) A person who is a dependent of another has a limited standard deduction. Married individuals filing separate returns when the other spouse itemizes and an individual filing a short period return may not take the standard deduction. There is nothing in the law that precludes an abandoned spouse from taking the standard deduction.
Page Ref.: I:2-12 and I:2-23 through I:2-24
Objective: 2
46) Husband and wife, who live in a common law state, are eligible to file a joint return for 2012, but elect to file separately. They do not have dependents. Wife has adjusted gross income of $25,000 and has $2,200 of expenditures which qualify as itemized deductions. She is entitled to one exemption. Husband deducts itemized deductions of $11,200. What is the taxable income for the wife?
A) $17,250
B) $19,000
C) $14,500
D) $22,800
Answer: B
Explanation: B) If one spouse on married filing separately returns itemizes deductions, the other spouse must also do so.
Page Ref.: I:2-12; Example I:2-5
Objective: 2
47) Lewis, who is single, is claimed as a dependent on his parents' tax return. He received $2,000 during the year in dividends, which was his only income. What is his standard deduction?
A) $950
B) $2,000
C) $2,300
D) $5,950
Answer: A
Explanation: A) For a dependent, the standard deduction is the greater of earned income plus $300 or $950. Dividends are unearned income.
Page Ref.: I:2-12; Example I:2-6
Objective: 2
48) Charlie is claimed as a dependent on his parents' tax return. He received $8,000 during the year from
a part-time acting job, which was his only income. What is his standard deduction?
A) $950
B) $5,950
C) $8,000
D) $8,300
Answer: B
Explanation: B) For a dependent, the standard deduction is the greater of earned income plus $300 or $950, but no more than the current year regular standard deduction amount. For 2012, the maximum standard deduction for a single person is $5,950.
Page Ref.: I:2-12; Example I:2-7
Objective: 2
49) Deborah, who is single, is claimed as a dependent on her parents' tax return. She had a part-time job during 2012 and earned $850 during the year, which was her only income. What is her standard deduction?
A) $850
B) $950
C) $1,150
D) $5,950
Answer: C
Explanation: C) For a dependent, the standard deduction is the greater of earned income plus $300 ($850 + 300 = $1,150) or $950.
Page Ref.: I:2-12; Example I:2-7
Objective: 2
50) Cheryl is claimed as a dependent on her parents' tax return. She had a part-time job during 2012 and earned $4,900 during the year, which was her only income. What is her standard deduction?
A) $950
B) $4,900
C) $5,200
D) $5,950
Answer: C
Explanation: C) $4,900 + 300 = $5,200. For a dependent, the standard deduction is the greater of earned income plus $300 or $950, up to a maximum of the regular standard deduction.
Page Ref.: I:2-12; Example I:2-7
Objective: 2
51) A married person who files a separate return can claim a personal exemption for his spouse if the spouse is not the dependent of another and has
A) gross income that is less than the personal exemption.
B) adjusted gross income that is less than the personal exemption.
C) no gross income.
D) no taxable income.
Answer: C
Explanation: C) A married person who files a separate return can claim a personal exemption for his spouse if the spouse has no gross income during the year and the spouse is not the dependent of another taxpayer.
Page Ref.: I:2-12
Objective: 2
52) Ben, age 67, and Karla, age 58, have two children who live with them and for whom they provide total support. Their daughter is 21 years old, blind, is not a full-time student and has no income. Her twin brother is 21 years old, has good sight, is a full-time student and has income of $3,900. Ben and Karla can claim how many personal and dependency exemptions on their tax return?
A) 2
B) 3
C) 4
D) 5
Answer: C
Explanation: C) Ben and Karla get two personal exemptions for themselves. Although their daughter is not their qualifying child, she still qualifies as a dependent since she meets all of the dependency tests for a qualifying relative. Their son qualifies as their dependent as he is their qualifying child and need not meet the gross income test. Therefore, they are entitled to a total of four personal and dependency exemptions.
Page Ref.: I:2-13 and I:2-14
Objective: 2
53) Sarah, who is single, maintains a home in which she, her 15-year old brother, and her 21-year-old niece live. Sarah provides the majority of the support for her brother, her niece, and her cousin, age 18, who is enrolled full-time at the university and lives in an apartment. While the niece and cousin have no income, her brother has a part-time job and earns $4,000 per year. How many personal and dependency exemptions may Sarah claim?
A) 1
B) 2
C) 3
D) 4
Answer: C
Explanation: C) Sarah may claim one personal exemption and two dependency exemptions for her niece and brother. Because her brother qualifies as her qualifying child for purposes of the dependency exemption, he does not have to meet the gross income test. Sarah may not claim her cousin as a dependent since her cousin does not live with her.
Page Ref.: I:2-13 and I:2-14
Objective: 2
54) Anita, who is divorced, maintains a home in which she and her 16 year old daughter live. Anita provides the majority of the support for her daughter and for a son, age 23, who is enrolled part-time at the university and lives in the dorm. The son also works in the campus bookstore and earns spending money of $4,000. How many personal and dependency exemptions may Anita claim?
A) 1
B) 2
C) 3
D) 4
Answer: B
Explanation: B) Anita will claim herself and her daughter who is a qualifying child. Anita's son does not qualify as her qualifying child as she fails age test, nor does he qualify as a dependent due to failing the gross income test.
Page Ref.: I:2-13 and I:2-14
Objective: 2
55) Amber supports four individuals: Erin, her stepdaughter, who lives with her; Amy, her cousin, who lives in another state; Britney, her friend, who lives legally in Amber's home all year long; and Charlie, her father, who lives in another state. Assume that the dependency requirements other than residence are all met. How many personal and dependency exemptions may Amber claim?
A) 2
B) 3
C) 4
D) 5
Answer: C
Explanation: C) Amber may claim one personal exemption and three (Erin, Britney, Charlie) dependency exemptions. Amy, her cousin, does not qualify because a cousin is not a related party and can only qualify as a dependent is she lives in the taxpayer's home all year long.
Page Ref.: I:2-13 and I:2-14
Objective: 2
56) John supports Kevin, his cousin, who lived with him all year. John also supports three other individuals who do not live with him:
Donna, who is John's mother
Melissa, who John's stepsister
Morris, who is Kevin's brother.
Assume that Donna, Melissa, Morris and Kevin each earn less than $3,950. How many personal and dependency exemptions may John claim?
A) 2
B) 3
C) 4
D) 5
Answer: C
Explanation: C) John may claim one personal exemption and three dependency exemptions for Kevin, Donna, and Melissa. Morris is John's cousin and does not qualify as a dependent since he doesn't live in John's home. A cousin is not related for tax purposes and would have to live in the taxpayer's home to be claimed as a dependent.
Page Ref.: I:2-13 and I:2-14
Objective: 2
57) Julia provides more than 50 percent of the support for three individuals: Theresa, an unrelated child who lives with Julia all year long; Margaret, Julia's cousin, who lives in another city; and Emma, Julia's daughter who lives in her own home. Each of the potential dependents earned less than $3,950. How many dependency exemptions can Julia claim on her 2012 tax return?
A) 0
B) 1
C) 2
D) 3
Answer: C
Explanation: C) (Theresa, Emma) Assuming all other tests are met, Theresa qualifies as Julia's dependent.
A person who lives with the taxpayer all year long need not be related to the taxpayer. Margaret does not qualify as Julia's dependent. She is not related for tax purposes and, therefore, can't be Julia's dependent unless she lives with Julia all year long. Emma qualifies as Julia's dependent. Since Emma is Julia's daughter, she is related for tax purposes and need not live with Julia to be claimed as Julia's dependent. Therefore, Julia has two dependents.
Page Ref.: I:2-13 and I:2-14
Objective: 2
58) Tony supports the following individuals during the current year: Miranda, his former mother-in-law who lives in her own home and has no gross income; his cousin, Jeff, age 23, who is a full-time student, earns $7,000 during the year, and lives with Tony all year long; and Matt, age 22, who is Tony's brother, is a full-time student living on campus and earns $8,000 during the year. How many dependency exemptions may Tony claim?
A) 0
B) 1
C) 2
D) 3
Answer: C
Explanation: C) Miranda qualifies as Tony's dependent. She is related to him for tax purposes and does not have to live with him. Jeff earns too much gross income (more than the personal exemption amount) and can not qualify as Tony's dependent. Although Matt earns more gross income than the personal exemption amount, he is considered Tony's qualifying child and, therefore, does not have to meet the gross income test. Therefore, Tony can claim two dependents.
Page Ref.: I:2-14; Examples I:2-10 and I:2-11
Objective: 2
59) David's father is retired and receives $14,000 per year in social security benefits. David's father saves $4,000 of the benefits and spends the remaining $10,000 for his support. How much support must David provide for his father to meet the dependent support requirement?
A) $10,000
B) $10,001
C) $14,000
D) $14,001
Answer: B
Explanation: B) The amount that David's father saves is not counted in the support test. Therefore, David need only provide $1 more than his father ($10,000 + $1) to meet the more than 50 percent test.
Page Ref.: I:2-15; Example I:2-13
Objective: 2
60) Which of the following is not considered support for the dependent support test?
A) food
B) clothing
C) rental value of lodging
D) value of services rendered by the taxpayer for the dependent
Answer: D
Explanation: D) Food, clothing, and the rental value of the lodging are all considered support.
Page Ref.: I:2-15
Objective: 2
61) Juanita's mother lives with her. Juanita purchased clothing for her mother costing $1,000 and provided her with a room that Juanita estimates she could have rented for $4,000. Juanita spent $5,000 on groceries she shared with her mother. Juanita also paid $700 for her mother's life insurance coverage. How much of these costs is considered support?
A) $5,000
B) $7,500
C) $10,000
D) $10,700
Answer: B
Explanation: B) $1,000 + $4,000 + .5(5,000) = $7,500. Life insurance premiums are not considered support. Page Ref.: I:2-15; Example I:2-14
Objective: 2
62) Anna is supported entirely by her three sons John, James, and Joseph who provide for her support in the following percentages:
John: 10%, James: 40%, Joseph: 50%
Assuming a multiple support declaration exists, which of the brothers may claim his mother as a dependent?
A) any of the sons
B) James or Joseph
C) Joseph only
D) None of them
Answer: B
Explanation: B) Although no one provides more than 50 percent of Anna's support, a qualifying pool of individuals (John, James, and Joseph) provide over 50 percent of Anna's support. Any one of them who provides more than 10 percent (James or Joseph) may claim Anna assuming a multiple support agreement is filed.
Page Ref.: I:2-17
Objective: 2
63) Blaine Greer lives alone. His support comes from the following sources:
Assuming a multiple support declaration exists, which of the individuals may claim Blaine as a dependent?
A) Ken or Martha
B) Buddy, Ken, or Martha
C) Ken, Martha, or Natalie
D) None of them
Answer: B
Explanation: B) A qualifying pool of individuals (Buddy, Ken, and Martha) provides more than 50 percent of Blaine's support. Natalie is not part of the qualifying pool as she could not otherwise claim Blaine because he is not related to her and does not live in her home. Of the qualifying pool, any individual who provides more than 10 percent of Blaine's support (Buddy, Ken or Martha) may claim Blaine under a multiple support agreement.
Page Ref.: I:2-17; Example I:2-17
Objective: 2
64) The child credit is for taxpayers with dependent children under the age of
A) 14.
B) 17.
C) 19.
D) 24.
Answer: B
Explanation: B) Children must be under age 17 to qualify.
Page Ref.: I:2-19
Objective: 2
65) Steven and Susie Tyler have three dependent children ages 13, 15, and 17. Their modified AGI for 2012 is $108,000. What is the amount of the child credit to which they are entitled?
A) $-0-
B) $1,950
C) $2,000
D) $3,000
Answer: C
Explanation: C) 2 × $1,000 = $2,000. Children age 17 and above do not qualify for the credit.
Page Ref.: I:2-19 and I:2-20
Objective: 2
66) Nate and Nikki have three dependent children ages 12, 15, and 17. Their modified AGI for 2012 is $120,000. What is the amount of the child credit to which they are entitled?
A) $-0-
B) $500
C) $1,500
D) $2,000
Answer: C
Explanation: C) The child credit before the phase out is $2,000 (2 × $1,000); the 17-year old does not qualify. They have excess AGI of $10,000 ($120,000 - $110,000). Their credit should be reduced by 10 ($10,000/$1,000) × $50 = $500. Thus, their child credit is $1,500.
Page Ref.: I:2-19 and I:2-20; Example I:2-22
Objective: 2
67) Ryan and Edith file a joint return for 2012 showing $130,000 of AGI (with no exclusions under Secs. 911, 931, and 933). They have three dependent children ages 7, 9, and 13. What is the amount of their child credit?
A) $0
B) $1,000
C) $2,000
D) $3,000
Answer: C
Explanation: C) The child credit is $1000 per qualifying child for 2012, with a phase-out for AGI exceeding $110,000 on joint returns. $130,000 - $110,000 = $20,000. There are twenty $1,000 increments (or parts thereof) exceeding the $110,000 phase-out floor, so the child credit will be reduced by 20 × $50 = $1,000. Credit before phase-out is 3 children × $1,000 = $3,000. After the phase-out the credit is $2,000 = $3,000 - $1000.
Page Ref.: I:2-19 and I:2-20; Example I:2-22
Objective: 2
68) Paul and Sally file a joint return for 2012 showing $87,000 of AGI (with no exclusions under Secs. 911, 931, and 933). They have three dependent children ages 6, 8, and 13. What is the amount of their child credit?
A) $0
B) $1,000
C) $2,000
D) $3,000
Answer: D
Explanation: D) Three children under the age of 17 and no phase-out. 3 × $1,000 = $3,000.
Page Ref.: I:2-19
Objective: 2
69) Amanda has two dependent children, ages 10 and 12. She earned $15,000 in 2012 from her waitress job. How much of her child credit is refundable?
A) $1,200
B) $1,500
C) $1,800
D) $2,000
Answer: C
Explanation: C) $1,800 = 15% × (15,000 - 3,000)
Page Ref.: I:2-19 and I:2-20; Example I:2-23
Objective: 2
70) You may choose married filing jointly as your filing status if you are married and both you and your spouse agree to file a joint return. Which of the following facts would prevent you from being considered married for filing purposes?
A) You were married for several years, but your divorce became final in December.
B) You are married but living apart until some problems can be solved.
C) Your spouse died during the year but the executor of the estate has agreed to the filing of a joint return.
D) None of the above.
Answer: A
Explanation: A) Marital status is determined as of the last day of the tax year. If the couple is divorced in December, then they are not married for tax purposes and may not file a joint return.
Page Ref.: I:2-21
Objective: 3
71) Tom and Alice were married on December 31 of last year. What is their filing status for last year?
A) They file as single.
B) They file as married joint or married separate.
C) They file as single for half the year and married for the other half.
D) They file as single for 364 days and married for one day.
Answer: B
Explanation: B) Marital status is determined as of the last day of the tax year. If the couple was married on December 31, they are considered married for the entire year and may file either married filing jointly or married filing separately.
Page Ref.: I:2-21
Objective: 3
72) When a spouse dies, the surviving spouse for the year of death
A) may file a married filing jointly return.
B) must file a tax return using the single filing status.
C) must file a tax return using the head of household filing status.
D) may file a married filing jointly return only if the death occurred in the last half of the year.
Answer: A
Explanation: A) In the year of death, a joint return can be filed.
Page Ref.: I:2-22; Example I:2-26
Objective: 3
73) In 2009, Leo's wife died. Leo has two small children, ages 2 and 4, living at home whom he supports entirely. Leo does not remarry and is not claimed as a dependent on another's return during any of this period. In 2010, 2011, and 2012, Leo's most advantageous filing status is, respectively
A) single for all three years.
B) head of household for all three years.
C) surviving spouse, surviving spouse, head of household
D) surviving spouse, surviving spouse, single.
Answer: C
Explanation: C) In the two years following death (2010 and 2011), Leo may file as surviving spouse as long as he has at least one dependent child living in the home during the entire year and he provides over half of the expenses of the home. After the two years following the year of death, Leo qualifies as head of household as he is unmarried and is maintaining a home for a qualifying individual (in this case, his qualifying child).
Page Ref.: I:2-22
Objective: 3
74) Carter dies on January 1, 2011. A joint return election is made in 2011 and Marjorie properly qualifies as a surviving spouse for the two following years. Marjorie has one child that she claims as a dependent for this same period. The number of personal and dependency exemptions allowed Marjorie in 2011 and in 2012 is, respectively
A) 1 and 1.
B) 2 and 2.
C) 3 and 2.
D) 3 and 3.
Answer: C
Explanation: C) Three exemptions for 2011 (joint return) and two for 2012 (surviving spouse).
Page Ref.: I:2-22
Objective: 3
75) Edward, a widower whose wife died in 2009, maintains a household for himself and his daughter who qualifies as his dependent. Edward's most favorable filing status for 2012 is
A) single.
B) surviving spouse.
C) head of household.
D) married filing jointly.
Answer: C
Explanation: C) Surviving spouse status is only available for the two years following the spouse's death, in this case, 2010 and 2011. However, Edward does qualify for head of household in 2012.
Page Ref.: I:2-22
Objective: 3
76) A surviving spouse is not required to
A) be remarried at the end of the year in which the surviving spouse status is claimed.
B) be a U.S. citizen or resident.
C) be qualified to file a joint return in the year of death.
D) have at least one dependent child living at home the entire year and pay over half of the expenses of the home.
Answer: A
Explanation: A) An individual claiming surviving spouse status cannot have remarried.
Page Ref.: I:2-22
Objective: 3
77) Which of the following dependent relatives does not have to live in the same household as the taxpayer who is claiming head of household filing status?
A) uncle
B) brother
C) father
D) nephew
Answer: C
Explanation: C) A taxpayer with a dependent parent qualifies as head of household even if the parent does not live with the taxpayer.
Page Ref.: I:2-23
Objective: 3
78) Sally divorced her husband three years ago and has not remarried. Since the divorce she has maintained her home in which she and her now sixteen-year-old daughter reside. The daughter is a qualified child. Sally signed the dependency exemption over to her ex-spouse. What is Sally's filing status for the current year and how many exemptions may she claim?
A) single and one
B) surviving spouse and one
C) head of household and one
D) head of household and two
Answer: C
Explanation: C) Sally qualifies as head of household for the current year. A taxpayer with a qualifying child satisfies the head of household requirement even if the taxpayer releases the dependency exemption to the child's other parent.
Page Ref.: I:2-23; Example I:2-27
Objective: 3
弹塑性力学总结汇编
弹塑性力学总结 弹塑性力学的任务是分析各种结构物或其构件在弹性阶段和塑性阶段的应力和位移，校核它们是否具有所需的强度、刚度和稳定性，并寻求或改进它们的计算方法。并且弹塑性力学是以后有限元分析、解决具体工程问题的理论基础，这就要求我们掌握其必要的基础知识和具有一定的计算能力。通过一学期的弹塑性力学的学习，对其内容总结如下： 一、弹性力学 1、弹性力学的基本假定 求解一个弹性力学问题，通常是已知物体的几何形状（即已知物体的边界），弹性常数，物体所受的外力，物体边界上所受的面力，以及边界上所受的约束；需要求解的是物体内部的应力分量、应变分量与位移分量。求解问题的方法是通过研究物体内部各点的应力与外力所满足的静力平衡关系，位移与应变的几何学关系以及应力与应变的物理学关系，建立一系列的方程组；再建立物体表面上给定面力的边界以及给定位移约束的边界上所给定的边界条件；最后化为求解一组偏分方程的边值问题。
在导出方程时，如果考虑所有各方面的因素，则导出的方程非常复杂，实际上不可能求解。因此，通常必须按照研究对象的性质，联系求解问题的范围，做出若干基本假定，从而略去一些暂不考虑的因素，使得方程的求解成为可能。 （1）假设物体是连续的。就是说物体整个体积内，都被组成这种物体的物质填满，不留任何空隙。这样，物体内的一些物理量，例如：应力、应变、位移等，才可以用坐标的连续函数表示。 （2）假设物体是线弹性的。就是说当使物体产生变形的外力被除去以后，物体能够完全恢复原来形状，不留任何残余变形。而且，材料服从虎克定律，应力与应变成正比。 （3）假设物体是均匀的。就是说整个物体是由同一种质地均匀的材料组成的。这样，整个物体的所有部分才具有相同的物理性质，因而物体的弹性模量和泊松比才不随位置坐标而变。 （4）假设物体是各向同性的。也就是物体内每一点各个不同方向的物理性质和机械性质都是相同的。 （5）假设物体的变形是微小的。即物体受力以后，整个物体所有各点的位移都小于物体的原有尺寸，因而应变和转角都远小于1。这样，在考虑物体变形以后的平衡状态时，可以用变
武汉大学弹塑性力学简答题以及答案
弹塑性力学简答题 2002年 1什么是偏应力状态？什么是静水压力状态？举例说明？ 静水压力状态时指微六面体的每个面只有正应力作用，偏应力状态是从应力状态中扣除静水压力后剩下的部分。 2从数学和物理的不同角度，阐述相容方程的意义。 从数学角度看，由于几何方程是6个，而待求的位移分量是3个，方程数目多于未知函数的数目，求解出的位移不单值。从物理角度看，物体各点可以想象成微小六面体，微单元体之间就会出现“裂缝”或者相互“嵌入”，即产生不连续。 3两个材料不同、但几何形状、边界条件及体积力（且体积力为常数）等都完全相同的线弹性平面问题，它们的应力分布是否相同？为什么？ 相同。应力分布受到平衡方程、变形协调方程及力边界条件，未涉及本构方程，与材料性质无关。 4虚位移原理等价于哪两组方程？推导原理时是否涉及到物理方程？该原理是否适用于塑性力学问题？ 平衡微分方程和静力边界条件。不涉及物理方程。适用于塑性力学问题。 5应力状态是否可以位于加载面外？为什么？ 不可以。保证位移单值连续。连续体的形变分量、、不是互相独立的，而是相关，否则导致位移不单值，不连续。 6什么是加载？什么是卸载？什么是中性变载？中性变载是否会产生塑性变形？加载：随着应力的增加，应变不断增加，材料在产生弹性变形的同时，还会产生新的塑性变形，这个过程称之为加载。
卸载：当减少应力时，应力与应变将不会沿着原来的路径返回，而是沿接近于直线的路径回到零应力，弹性变形被恢复，塑性变形保留，这个过程称之为卸载。 中性变载：应力增量沿着加载面，即与加载面相切。应力在同一个加载面上变化，内变量将保持不变，不会产生新的塑性变形，但因为应力改变，会产生弹性应变。 7用应力作为未知数求解弹性力学问题时，应力除应满足平衡方程外还需要满足哪些方程？协调方程和边界条件。 8薄板弯曲中，哪些应力和应变分量较大？哪些应力和应变分量较小？ 平面内应力分量最大，最主要的是应力，横向剪应力较小，是次要的应力；z方向的挤压应力最小，是更次要的应力。 9什么是滑移线？物体内任意一点沿滑移线的方向的剪切应力是多少？ 在塑性区内，将各点最大剪应力方向作为切线而连接起来的线，称之为滑移线。 剪切应力是最大剪应力。 10什么是随动强化？试用单轴加载的情况加以解释？ 2004 1对于各项同性线弹性材料，应用广义胡克定律说明应力与应变主轴重合？ ，当某个面上的剪切应力为零时，剪应变也为零，这说明应力的主方向与应变的主方向重合。 2应力边界条件所描述的物理本质是什么？ 物体边界点的平衡条件。 3虚位移原理等价于哪两组方程？这说明了什么？
治疗龋齿的方法有哪些
治疗龋齿的方法有哪些 治疗龋齿的方法有哪些 一、针刺治疗 实火痛，上齿取下关、内庭，下齿痛取颊车、合谷，均宜用泻法，留针10～15分钟。虚火痛者，在上方基础上加补太溪穴、泻行间穴 一定要分清虚实，不可混淆。 二、中药治疗 1、若齿龈红肿热痛或有寒热，口有秽臭，或齿孔出脓，苔黄腻，脉弦数者，为风热实火，治以清泄阳明实热。方用：生石膏30克、 竹叶6克、生山栀9克、银花16克、连翘15克、赤芍10克、胡黄 连9克、黄芩9克，水煎服。 2、若齿龈不肿，其痛日轻夜重，徽寒不热，口无秽臭，齿根龋 齿易于动摇，舌红少苔，脉弦细数者，为阴虚火旺，治宜滋阴降火。方用：生地25克、玄参10克、麦冬12克、丹皮9克、知母9克、 黄柏6克、川牛膝9克、金石斜10克、肉桂3克，水煎服。龋齿西 医治疗方法 三、药物治疗 1、药物治疗是在磨除龋坏的基础上，应用药物抑制龋病发展的 方法，适用于恒牙尚未成洞的浅龋，乳前牙的浅、中龋洞。常用药 物包括氨销酸银和氟化钠等。 2、先将龋坏组织尽可能磨除，并磨去洞缘牙齿薄片，使洞敞开;以棉条隔离唾液，擦干牙面后以小棉球蘸氨硝酸银溶液涂擦龋坏牙 面1-2分钟，温热气体的枪吹干再涂，如此两次，然后以蘸丁香油 小棉球涂擦，使之还原成黑色，吹干即完成治疗。所形成的还原银 沉淀于牙本质小管中阻塞牙本质小管，阻止龋的发展。一般每周进 行1次，3-4次为一疗程，3-6月后复查，治疗中应防止灼伤软组织。
四、银汞合金充填术 1、对已形成实质性缺损的牙齿，充填术是目前应用最广泛且成 效较好的方法，其基本过程可分为两步：先去除龋坏组织和失去支 持的薄弱牙体组织，并按一定要求将窝洞制成合理的形态。然后以 充填材料填充恢复其固有形态和功能。适用于充填后牙和隐蔽部位 的'前牙洞。 2、窝洞制备基本原则：去净龋坏组织，防止继发龋。制洞作用 之一类似清创，须去除龋坏组织，使窝洞建立在健康的牙体组织上，防止继发性感染。 3、由于牙齿修复后需承担咀嚼功能，因此充填修复后应达到两 方面要求，一方面能长期保持修复物不致松动、脱落，即应具有固 位形;另一方面修复物和剩余牙体组织都不致因承受咀嚼力而碎裂， 即应具有抗力形。更重要的是，二者在窝洞制备时应同时兼顾。 4、充填术修复过程(银汞合金)：去除龋坏组织，建立窝洞外形;制备抗力形和固位;洞形修整和窝洞清理;窝洞清毒;垫基底;充填银 汞合金;抛光。 五、复合树脂充填术 适用于充填前牙和不承受咀嚼力量的后牙洞，充填要点有： ①制备一定的洞形 ②中度以上的窝洞需作基底 ③调拌器具要洁干燥。使用非金属调拌刀，注意组分的配比，充分调拌均匀。 ④充填时防湿，避免产生气泡，并宜用聚脂薄膜或玻璃纸将材料压紧，最后修形磨光。 六、酸蚀法光敏复合树脂充填术 适应证同复合树脂充填术，还适用于牙体缺损较多、固位较差和遮盖变色牙等。充填要点有：
应用弹塑性力学习题解答
应用弹塑性力学习题解答 目录 第二章习题答案 设某点应力张量的分量值已知，求作用在过此点平面上的应力矢量，并求该应力矢量的法向分量。 解该平面的法线方向的方向余弦为 而应力矢量的三个分量满足关系 而法向分量满足关系最后结果为 利用上题结果求应力分量为时，过平面处的应力矢量，及该矢量的法向分量及切向分量。 解求出后，可求出及，再利用关系
可求得。 最终的结果为 已知应力分量为，其特征方程为三次多项式，求。如设法作变换，把该方程变为形式，求以及与的关系。 解求主方向的应力特征方程为 式中：是三个应力不变量，并有公式 代入已知量得 为了使方程变为形式，可令代入，正好项被抵消，并可得关系 代入数据得，， 已知应力分量中，求三个主应力。 解在时容易求得三个应力不变量为， ，特征方程变为 求出三个根，如记，则三个主应力为 记 已知应力分量 ，是材料的屈服极限，求及主应力。 解先求平均应力，再求应力偏张量，， ，，，。由此求得 然后求得，，解出 然后按大小次序排列得到 ，，
已知应力分量中，求三个主应力，以及每个主应力所对应的方向余弦。 解特征方程为记，则其解为，，。对应于的方向余弦，，应满足下列关系 （a） （b） （c） 由（a）,(b)式，得，，代入（c）式，得 ，由此求得 对，，代入得 对，，代入得 对，，代入得 当时，证明成立。 解 由，移项之得 证得 第三章习题答案 取为弹性常数，，是用应变不变量表示应力不变量。
解：由，可得， 由，得 物体内部的位移场由坐标的函数给出，为， ，，求点处微单元的应变张量、转动张量和转动矢量。 解：首先求出点的位移梯度张量 将它分解成对称张量和反对称张量之和 转动矢量的分量为 ，， 该点处微单元体的转动角度为 电阻应变计是一种量测物体表面一点沿一定方向相对伸长的装置，同常利用它可以量测得到一点的平面应变状态。如图所示，在一点的3个方向分别粘贴应变片，若测得这3个应变片的相对伸长为，，，，求该点的主应变和主方向。 解：根据式先求出剪应变。考察方向线元的线应变，将，，，，，代入其 中，可得 则主应变有 解得主应变，，。由最大主应变可得上式只有1个方程式独立的，可解得与轴的夹角为 于是有，同理，可解得与轴的夹角为。 物体内部一点的应变张量为 试求：在方向上的正应变。
龋病治疗
龋病治疗 龋病在治疗过程中若判断不当或技术不精细，都可能出现失误引起后遗症，给患者带来不必要的痛苦。充分认识这个问题并及时予以避免，是十分必要的。在临床工作中经常会遇到以下几种情况，分别谈谈笔者的体会和意见。 1意外穿髓 在龋洞洞形制备过程中，本来不应穿通髓腔但因处理不当而使健康牙髓暴露称意外穿髓。穿髓给患者身心带来痛苦，同时使治疗变得更复杂。穿髓的常见原因有：对患牙髓腔解剖知识掌握不足，髓腔状况与患者年龄和患牙牙龄有密切关系，一般年轻人髓腔大髓角高，尤以近中颊髓角高，术者应熟悉有关牙体解剖知识，手术时心中有数；操作粗疏，不够仔细，对急性龋，龋坏软面呈大片状，宜用挖器，并逐层去除。对慢性龋，最好采用大号球钻慢速提磨，不宜用涡轮机去除深洞软龋。深洞不应把洞底制平而应把
底垫平。制洞过程是很精细的手术，必须小心谨慎，以免穿髓；髓角变异，一般说来，牙髓的髓角所居位置，约在釉牙本质界内 4～5mm，偶尔有髓角在釉牙本质界内1～2mm，甚至接近釉牙本质界的情况，这种出于常规意外的变异则不易防范。穿髓的处理：意外穿髓所暴露牙髓多为正常牙髓，可根据患者年龄而决定治疗方案。青少年可做直接盖髓术；成年人可根据穿髓孔的大小而定，穿孔小者可试作直接盖髓，穿孔大者则失活牙髓作干髓术或切髓术，前牙作牙髓摘除术；老年人只能作干髓术或牙髓摘除术。 2充填物折裂、松脱 充填物在口腔内经过一段时间后产生 折裂或松脱，其原因有：洞制备因素，洞深度不够或垫底太厚，致充填体太薄，不能承担咀嚼压力而碎裂；承担力区制备不良；邻面鸠尾峡过窄过浅，轴髓线角过锐，龈壁倾斜而不能承力［1］;充填体固位不良，如洞口略大于洞底未成盒状，邻面洞无鸠尾固位形，无邻面梯形及其他附加固位形；材料制备因素：调拌中成分比例不当，银汞合金的
龋病的病因、发生发展、治疗及预防
龋病的病因、发生发展、治疗及预防 龋病的病因、发生发展、治疗及预防 病因病理 龋病经过长期研究，现已基本明了，龋病是由多种因素复合作用所致，目前公认的龋病病因学说是四联因素学说，主要包括细菌、 口腔环境、宿主和时间，其基本点为：致龋性食物(特别是蔗糖和精 制碳水化合物)在糖，紧紧贴附于牙面由涎液蛋白形成的获得性膜上，在这种由牙齿表面解剖结构和生化、生物物理特点形成的不仅得以 牢固的附着于牙面，而且可以在适宜温度下，有足够的时间在菌斑 深层产酸，侵蚀牙齿，使之脱矿，并进而破坏有机质，产生龋洞。 1.细菌 是龋病发生的必要条件，一般认为致龋菌有两种类型，一种是产酸菌属，其中主要为变形链球菌、放线菌属和乳杆菌，可使碳水化 合物分解产酸，导致牙齿 无机质脱矿;另一种是革兰氏阳性球菌，可破坏有机质，经过长 期作用可使牙齿形成龋洞。目前公认的主要致龋菌是变形链球菌， 其它还包括放线菌属、乳杆菌等。 细菌主要是借助菌斑粘附于牙面。口腔滞留食物中的碳水化合物被降解后，一方面聚合产生高粘性葡聚糖，形成菌斑基质，另一方 面产酸使牙齿脱矿，菌斑的组成比较复杂，除大量细菌外，还有糖、蛋白、酶等物质。 2.口腔环境 口腔是牙齿的外环境，与龋病的发生密切相关，其中起主导作用的主要是食物和涎液。 (1)食物主要是碳水化合物，既与菌斑基质的形成有关，也是菌 斑中细菌的主要能源，细菌能利用碳水化合物(尤其是蔗糖)代谢产
生酸，并合成细胞外多糖和细胞内多糖，所产的有机酸有利于产酸 和耐酸菌的生长，也有利于牙体硬组织的脱矿，多糖能促进细菌在 牙面的粘附和积聚，并在外源性糖缺乏时，提供能量来源。因此， 碳水化合物是龋病发生的物质基础。 (2)涎液在正常情况下，涎液有以下几种作用： 机械清洗作用减少细菌的积聚。 抑菌作用直接抑菌或抑制菌斑在牙面的附着。 抗酸作用由所含重碳酸盐类等物质起中和作用。 抗溶作用通过所含钙、磷、氟等增强牙齿抗酸能力，减少溶解度。 涎液的量和质发生变化时，均可影响龋患率，临床可见，口干症或有涎液分泌的患者龋患率明显增加。颌面部放射治疗患者可因涎 腺被破坏而有多个牙龋;另一方面，当涎液中乳酸量增加，或重碳酸 盐含量减少时，也有利于龋的发生。 3.宿主 牙齿是龋病过程中的靶器官，牙齿的形态、矿化程度和组织结构与龋病发生有直接关系，如牙齿的窝沟处和矿化不良的牙较易患龋，而矿化程度较好、组织内含氟量适当的牙抗龋力较强;另方面，牙齿 的结构与机体有密切关系，尤其是在发育中，不仅影响到牙齿的发 育和结构，而且对涎液的流量、流速及其组成也有很大影响，因而 也是龋病发生中的重要环节。 4.时间 龋病的发生有一个较长的过程，从初期龋到临床形成龋洞一般需1.5-2年，因此即使致龋细菌、适宜的环境和易感宿主同时存在， 龋病也不会立即发生，只有上述三个因素同时存在相当长的时间， 才可能产生龋坏，所以时间因素在龋病发生中具有重要意义。 发展过程
儿童龋病的发展历程及其治疗方案综述
儿童龋病的发展历程及其治疗方案 一、儿童龋病在病因学及组织病理学特征方面与成人并无显著差 肯定没戏异，其发展历程为 ⑴牙齿硬组织发生病变时，首先是变浊变软，其次为色素沉着，最终发生崩解，形成龋洞。变浊变软即牙组织失去原有的光泽和透明度。 ⑵当牙釉质发生龋病时，组织内发生脱矿现象，将牙釉质内的磷灰石结晶破坏，晶体的排列也紊乱了，造成折光性能的改变，牙釉质呈白垩色，此时的初期，脱矿现象发生在牙釉质表层下，牙齿表面仍然完整，继而在咀嚼压力和其他因素的影响下，才出现牙体的破坏和崩解。 ⑶由于牙釉质硬度大，富含矿物质，此时病程进展缓慢。当龋病发展到牙本质，沿牙釉质牙本质界横向扩大，同时向深处发展，牙本质脱矿而透明度减低，牙本质变软，由于牙本质内的有机物含量较多，此时病程进展较快。 ⑷由于外界的色素物质通过裂缝和小孔进入牙釉质内的损害区，早期牙釉质龋为褐色。当病变进入牙本质，牙体内矿物质溶解，牙本质内蛋白质发生破坏和分解，产生色素沉着，加上外界的和细菌产生的色素物质浸入牙本质，使其变为褐色、黑褐色，甚者黑色。 ⑸当龋病病变加重时，病变部位就会发生崩解，形成龋洞。初期为隐匿性龋，咬牙合面点隙沟裂病变呈外窄内宽的损害，到达牙本质继续向深处及四周发展，牙齿表面仍然完整。后因表面牙釉质失去支持，稍受力就会断裂，变为开放性损害。 但因为儿童生长发育和牙齿生理和解剖的特点，致使儿童龋病与成人
相比病损波及范围更广泛，进展迅速且危害更大。 乳牙龋病：儿童龋病包括乳牙龋病和年轻恒牙龋病。 （一）患病状况 ⑴好发部位：以上颌乳切牙和下颌乳磨牙多见，其次是上颌乳磨牙、 ⑵上颌乳尖牙，下颌乳尖牙和下颌乳切牙较少。 ⑶各年龄段的乳牙龋病发生部位有明显的特点。1~2岁时，主要发生于上颌乳前牙的唇面和邻面；3~4岁时，多发的是乳磨牙合面的窝沟；4~5岁时，好发于乳磨牙的邻面。 （二）常见患病类型 1.低龄儿童龋（ECC）：小于6岁的儿童，只要在任何一颗乳牙上出现一个或一个一上的龋（无论是否成为龋洞）、失（因龋所致）、补牙面，即为低龄儿童龋。 2.喂养龋：是低龄儿童龋的一种，主要由于不良的喂养习惯所致。包括：含奶瓶入睡、牙齿萌出后喂夜奶、延长母乳或奶瓶喂养时间、过多饮用含糖饮料等。 3.环形龋：乳前牙唇面、邻面龋较快发展成围绕牙冠的广泛性的环形龋，呈卷脱状。环状龋多见于牙冠中1/3至颈1/3处，有时切缘残留少许正常的釉质、牙本质。 4.猖獗性龋：Massler把突然发生、涉及牙面广泛，迅速形成龋洞，早期波及牙髓，且常常发生在不易患龋的牙位或牙面上，如下颌前牙的唇面、近切端部位。
龋齿治疗的方法有哪些
龋齿治疗的方法有哪些 龋齿在人们生活中是很常见，在出现龋齿后要抓紧时间治疗。那么，龋齿治疗的方法有哪些呢？本文就给大家介绍一些龋齿的治疗方法，希望对大家有所帮助。 龋齿治疗的方法有哪些 龋齿也就是平时所说的“虫牙”，这是困扰了很多人的一种牙齿疾病，很多人都想要知道的是，龋齿治疗有哪些？什么样的方法能够更好的治疗龋齿呢？下面就一起来看看吧。 1、龋坏组织磨除法：适用于龋坏面积广泛，如整个咬合面龋坏以及牙釉质或牙本质层剥落，不能制成补牙洞形的牙齿。重点磨除过锐的牙尖、牙边缘和表层龋坏组织，达到阻止龋坏继续发展的目的。 2、药物疗法：适用于龋环比较浅，还没有形成龋洞的初期龋。使用的药物是氨硝酸银。采用氨硝酸银棉球涂擦龋坏病变组织，一般反复涂擦1-2分钟，用热气吹拂、吹干后再重复1次，再吹干，以达到药物治疗龋病组织的目的。 3、氨硝酸银棉球涂擦过的龋坏组织，一般使用丁香油或10%福尔马林棉球涂擦产生银黑色，并能形成蛋白银和还原银，沉积到牙本质小管内，堵塞牙本质小管，并导致牙本质小管内的细菌停止繁殖，最终达到阻止龋病发展。药物疗法常常与龋坏组织磨除法结合治疗，效果更好。
4、龋坏组织再矿化法：指的是通过人工配制钙、磷、氟化物的矿化液作用于牙齿，使牙齿病变区组织发生矿物化，也就是使矿化液中的钙、磷、氟化物渗透到牙齿病变区。这种能使病变区组织重新获得矿物质的过程，称为再矿化。龋坏组织再矿化方法适用于初期龋。具体方法是使用人工配制的矿化液含漱。临床上，使用再矿化方法治疗初期龋，可使白垩色缩小，或停止发展。再矿化疗法方法简单，效果好，没有痛苦而且安全。 5、龋坏组织充填法；是治疗龋坏组织最常用的方法。适用于牙齿龋坏后能制作固位洞形的牙齿。利用补牙洞型将充填材料固定在牙齿上，恢复牙齿的缺损和功能，以保持牙齿外形，维护牙列的完整性。 了解龋齿治疗方法，儿童龋齿的预防有哪些 1、孕期保健要做好。多吃蔬菜、水果、茶、牛奶等含有一定量氟化物的食物和饮料，对小儿将来的牙齿发育和减少龋齿发生的机会，都有明显的好处。 2、避免婴幼儿的“奶瓶综合征”。还要纠正吮指等口腔不良习惯。 3、父母应为乳婴儿刷牙。在婴儿乳牙萌出前，父母可用一块长宽各约5厘米正方形的纱布蘸淡盐水，轻轻擦拭，将婴儿的牙龈上的菌斑去除。 4、对新萌出的恒磨牙和前磨牙进行窝沟封闭。
龋齿的治疗(专业研究)
龋齿的治疗 龋齿的治疗概要： 龋齿的治疗原则是针对不同程度的龋损，采用不同的治疗方法。对于牙釉质龋可以用保守疗法，如化学疗法、再矿化法、窝沟封闭等。对于有龋损的患牙进行充填修复治疗。对深的龋洞先抚髓，如氢氧化钙糊剂衬垫，再修复治疗。 龋齿的详细治疗： 治疗对策 （一）治疗原则 龋病治疗的目的在于终止病变的发展，保护牙髓，恢复牙的形态、功能及美观，并维持与邻近软硬组织的正常生理解剖关系。 龋病的治疗原则是针对不同程度的龋损，采用不同的治疗方法。对于早期釉质龋采用保守治疗，有组织缺损时用修复性方法治疗。深龋时先采用保护牙髓的措施，再进行修复治疗。 （二）治疗计划 根据龋损的程度不同，制定不同的治疗计划。对于牙釉质龋可以用保守疗法，如化学疗法、再矿化法、窝沟封闭等；对于有龋损的患牙进行充填修复治疗；对深的龋洞先抚髓，如氢氧化钙糊剂衬垫，再修复治疗。 （三）治疗方案 1.保守疗法 （1）化学疗法 用化学药物处理龋损.使病变终止或消除的方法。该方法主要用于：①恒牙
早期釉质龋、尚未形成龋洞者；②乳前牙邻面浅龋及乳牙骀面广泛性浅龋，1年内将替换者；③静止龋。常用的化学疗法的药物为氟化物（75%氟化钠甘油糊剂，8%氟化亚锡溶液.酸性磷酸氟化钠溶液，含氟凝胶及含氟涂料），硝酸银（10%硝酸银和氨硝酸银）。 操作方法：①用牙钻磨去牙表面的浅龋，暴露病变部位，大面积碟状龋损可磨除边缘脆弱釉质；②清洁牙面.去除牙石和菌斑；③隔湿，吹干牙面；④涂布药物：氟化物，将氟制剂涂于患区，用橡皮杯或棉球反复涂撩牙面1～2分钟。硝酸银。用棉球蘸药涂布患牙区，热空气吹干后，再涂还原剂，重复几次，直至出现黑色或灰白色沉淀。 注意事项：①氟化物有毒勿吞入；②硝酸银腐蚀性大，使用时严格隔湿，防止与软组织接触。 （2）再矿化疗法 用人工的方法使已经脱矿、变软的釉质发生再矿化，恢复硬度，使早期釉质龋终止或消除的方法称再矿化治疗。主要用于光滑面早期釉质龋和龋易感者的防龋。再矿化液主要由钙、磷和氟组成.应用方法主要为含漱法和局部涂擦法。 （3）窝沟封闭 用封闭剂使窝沟与口腔环境隔绝，阻止细菌、食物残擅及其酸性产物等进入窝沟，达到防龋的效果。主要用于窝沟可凝龋和无龋的深沟裂。窝淘封闭剂的主要成分为树脂--双酚A甲基丙烯酸缩水甘油酯，操作与复合树脂修复相同。 2.修复性治疗 除早期釉质龋可用保守方法治疗外，一般说来，龋病都要用修复的方法治疗，
龋病学-龋病治疗
龋病学 第四章龋病治疗 口腔内科学教研室刘鸿雁 T e l：5358348 主要内容 ?非手术治疗 ?牙体修复的生物学基础 ? ?窝洞制备的基本原则 ?窝洞预备的基本步骤 ? ? ?玻璃离子修复术 ?深龋的治疗 ?龋病治疗的并发症与处理 龋病治疗概述 ?龋病是一种慢性细菌性、进行性疾病，不经治疗不会停止其破坏进程，治疗不彻底可再次发生。 ?一旦遭到破坏，不 能通过细胞再生来恢复 缺损的组织，必须用人 工材料来修复
龋病治疗概述 治疗的目的： 终止龋病过程，保护牙髓，恢复牙的形态、功能及美观，并维持临近软组织的正常生理解剖关系。 一、非手术治疗(保守治疗) 龋病的非手术治疗是采用药物或再矿化等保守方法使龋病病变终止或消除的治疗方法。 非手术治疗 适应症:早期龋，静止龋，要替换的乳牙， 无功能牙 1.药物疗法：氟化物，硝酸银涂擦 2.再矿化法:再矿化液(含钙,磷,氟)含漱 3.窝沟封闭:含氟封闭剂封闭合面无龋深 沟裂，起到屏障和再矿化作用 窝沟封闭方法： 二、窝洞充填术 充填术就是用手术的方法去除龋坏组织，制备洞形，选用适宜的修复材料修复组织缺损，终止龋病发展，恢复牙齿的
形态和功能。 牙体修复的生物学基础 ?牙是有感觉和代谢的活体组织，牙体修复是一生物性的治疗技术。 ?牙釉质：无细胞结构，但受到牙本质生理活动的影响。釉柱的排列方向对备洞非常重要。对釉质厚度的了解可帮助确定洞的深度和酸蚀粘结效果。 牙体修复的生物学基础 ?牙本质组织结构特点： 小管、细胞突、液体。 釉牙本质界小管占牙本 质表面积4%。近髓端小 管占牙本质表面积80%。 牙体修复的生物学基础 ?牙骨质： 牙体修复的生物学基础 ?牙周组织： 牙的支持组织，任何不当的充填治疗都会造成对牙周组织的创伤 牙体修复与材料选择原则 牙体修复与材料选择原则 ?牙体修复的原则 1.去净龋坏牙体组织、感染牙本质，消除感染源，终止龋病过程，避免产生继发龋。
(完整版)弹塑性力学作业(含答案)
2—15.如图所示三角形截面水坝材料的比重为γ，水的比重为γ1。己求得应力解为： σx =ax+by ，σy =cx+dy-γy ， τxy =-dx-ay ； 试根据直边及斜边上的边界条件，确定常数a 、b 、c 、d 。 解：首先列出OA 、OB 两边的应力边界条件： OA 边：l 1=-1 ；l 2=0 ；T x = γ1y ； T y =0 则σx =-γ1y ； τxy =0 代入：σx =ax+by ；τxy =-dx-ay 并注意此时：x =0 得：b=-γ1；a =0； OB 边：l 1=cos β；l 2=-sin β，T x =T y =0 则：cos sin 0cos sin 0x xy yx y σβτβτβσβ+=?? +=?………………………………（a ） 将己知条件：σx= -γ1y ；τxy =-dx ； σy =cx+dy-γy 代入（a ）式得： ()()() 1cos sin 0cos sin 0y dx b dx cx dy y c γβββγβ-+=???--+-=??L L L L L L L L L L L L L L L L L L 化简（b ）式得：d =γ1ctg 2β； 化简（c ）式得：c =γctg β-2γ1 ctg 3β 2—17.己知一点处的应力张量为3 1260610010000Pa ??????????? 试求该点的最大主应力及其主方向。 解：由题意知该点处于平面应力状态，且知：σx =12×103 σy =10×103 τxy =6×103，且该点的主应力可由下式求得： (()()3 1.2333 3 121010 2217.0831******* 6.082810 4.9172410 x y Pa σσσ?++?==????=?=±?=? 则显然：3 312317.08310 4.917100Pa Pa σσσ=?=?= σ1 与x 轴正向的夹角为：（按材力公式计算） ()22612sin 226 12102 cos 2xy x y tg τθθσσθ--?-++ ====+=--+ 显然2θ为第Ⅰ象限角：2θ=arctg （+6）=+80.5376° 则：θ=+40.2688B 40°16＇ 或（-139°44＇）
(完整版)弹塑性力学公式
应力应变关系: 弹性模量 || 广义虎克定律 1.弹性模量 a 弹性模量 单向拉伸或压缩时正应力与线应变之比,即 E σε = b 切变模量 切应力与相应的切应变 之比,即 G τγ= c 体积弹性模量 三向平均应力 0() 3 x y z σσσσ++= 与体积应变θ(=εx +εy +εz )之比, 即 K σθ= d 泊松比 单向正应力引起的横向线应变ε1的绝对值与轴向线应变ε的绝对值之比,即 1 ε νε= 2.广义虎克定律 a.弹性力学基本方程 在弹性力学一般问题中，需要确定15个未知量，即6个应力分量，6个应变分量和3个位移分量。这15个未知量可由15个线性方程确定，即 (1)3个平衡方程(或用脚标形式简)写 为: 22()0 j ij i i x u f t σρ??++-=?? (,,,)i j x y z = (2)6个变形几何方程,或简写为: 1()2j i ij j i u u E x x ??= +?? (,,,)i j x y z = (3)6个物性方程简写为: 0132ij ij E G E ν σσδ= - 2ij ij ij G σελθδ=+ (,,,)i j x y z = { 1() 0() () i j ij i j δ=≠= 2.边界条件 x x xx xy xy xz xz F l l l σττ=++ y yz xx y xy yz xz F l l l τσσ=++ z zz xx xy xy z xz F l l l ττσ=++ 式中，l nj =cos(n,j)为边界上一点的外 法线n 对j 轴的方向余弦 b 位移边界问题 在边界S x 上给定的几何边界条件为 *x x u u = * y y u u = *z z u u = 式中，u i 为表面上给定的位移分量 Cauchy 公式： T x = σ x l + τ xy m +τ zx n T y = τ xy l+σ y m +τ zy n T y =τ xz l+τ y z m +σ z n (n z n T n T στ= 边界条件： ()()()x xy xz s x xy y yz s y xz yz z s z l m n T l m n T l m n T στττστττσ++=++=++= 平衡微分方程： 000yx x zx x xy y zy y yz xz z z F x y z F x y z F x y z τσττστττσ???+++=??????+++=??????+++=??? 主应力、不变量，偏应力不变量 321231230 x y z x xy y z zx yz yx y zy xz x z x xy xz yx y yz zx zy z I I I I I I σσσσσσστσστττσττσσστττστττσ-+-==++=++ = 1231 ();3 m i i m s σσσσσσ=++=- ()()()1123222222230 16()6x y y z z x xy yz zx J s s s J J σσσσσστττ=++=??=-+-+-+++????=偏应力张量行列式的秩 八面体 812381 () 3σσσστ=++ 等效应力σ=体积应变x y z θεεε=++ 12312()E v v εσσσ-= ++ 几何方程： ;;;x xy y yz z xy u u v x y x v v w y z y w u w z z x εγεγεγ???= =+??????==+ ??????==+ ??? 1 2 ij ij εγ= 变形协调方程22 222y xy x xy y x ετε???+=??? 物理方程 ()()()12(1) ;12(1) ;12(1) ;x x y z xy xy y y x z yz yz z z y x zx zx v v E E v v E E v v E E εσσσγτεσσσγτεσσσγτ+??=-+=??+??=-+=??+??=-+=??
弹塑性力学讲义全套
弹塑性力学 弹塑性力学 绪论：弹性力学也称弹性理论，主要研究弹性体在外力作用或温度变化等外界因素下所产生的应力、应变和位移，从而解决结构或机械设计中所提出的强度和刚度问题。在研究对象上，弹性力学同材料力学和结构力学之间有一定的分工。材料力学基本上只研究杆状构件；结构力学主要是在材料力学的基础上研究杆状构件所组成的结构，即所谓杆件系统；而弹性力学研究包括杆状构件在内的各种形状的弹性体。 弹塑性力学是固体力学的一个重要分支，是研究弹性和塑形物体变形规律的一门学科。它推理严谨，计算结果准确，是分析和解决许多工程技术问题的基础和依据。在弹塑性力学中，我们可以看到很多学习材料力学、结构力学等学科所熟知的参数和变量，一些解题的思路也很类似，但是我们不能等同的将弹塑性力学看成材料力学或者是结构力学来学习。材料力学和结构力学的研究对象及问题，往往也是弹塑性力学所研究的对象及问题。但是，在材料力学和结构力学中主要采用简化的初等理论可以描述的数学模型；在弹塑性力学中，则将采用较精确的数学模型。有些工程问题（例如非圆形断面柱体的扭转、孔边应力集中、深梁应力分析等问题）用材料力学和结构力学的方法求解，而在弹塑性力学中是可以解决的；有些问题虽然用材料力学和结构力学的方法可以求解，但无法给出精确可靠的理论，而弹塑性力学则可以给出用初等理论所得结果可靠性与精确度的评价。在弹塑性力学分析中，常采用如下简化假设：连续性假设、均匀各向同性、小变形假设、无初应力假设等假设。 弹塑性力学基本方程的建立需要从几何学、运动学和物理学三方面来研究。在运动学方面，主要是建立物体的平衡条件，不仅物体整体要保持平衡，而且物体内的任何局部都要处于平衡状态。反映这一规律的数学方程有两类，即运动微分方程和载荷的边界条件。以上两类方程都与材料的力学性质无关，属于普适方
弹塑性力学习题题库加答案
第二章 应力理论和应变理论 2—3．试求图示单元体斜截面上的σ30°和τ30°（应力单位为MPa ）并说明使用材料力学求斜截面应力为公式应用于弹性力学的应力计算时，其符号及 306.768 6.77() 104 sin 2cos 2sin 602cos 6022 1 32 3.598 3.60() 22 x y xy MPa MPa σστατα=----+= ?+= ?-=-?-?=-- 代入弹性力学的有关公式得： 己知 σx = -10 σy = -4 τ xy = +2 3030( )cos 2sin 22 2 1041041cos 602sin 607322226.768 6.77()104 sin 2cos 2sin 602cos 602 2 1 32 3.598 3.60()2 x y x y xy x y xy MPa MPa σσσσσατα σστατα+-= ++---+= ++=--?+=----+=- ?+=- ?+=+?= 由以上计算知，材力与弹力在计算某一斜截面上的应力时，所使用的公式是不同的，所得结果剪应力的正负值不同，但都反映了同一客观实事。 2—6. 悬挂的等直杆在自重W 作用下（如图所示）。材料比重为γ弹性模量为 E ，横截面面积为A 。试求离固定端z 处一点C 的应变εz 与杆的总伸长量Δl 。 解：据题意选点如图所示坐标系xoz ，在距下端（原点）为z 处的c 点取一截面考虑下半段杆的平衡得： 题图 1-3
c 截面的内力：N z =γ·A ·z ； c 截面上的应力：z z N A z z A A γσγ??= ==?； 所以离下端为z 处的任意一点c 的线应变εz 为： z z z E E σγε= = ； 则距下端（原点）为z 的一段杆件在自重作用下，其伸长量为： ()2 2z z z z z z z z y z z l d l d d zd E E E γγ γε=???=??=? = ?= ； 显然该杆件的总的伸长量为（也即下端面的位移）： ()2 222l l A l l W l l d l E EA EA γγ?????=??= = = ；（W=γAl ） 2—9.己知物体内一点的应力张量为：σij =50030080030003008003001100-????+-?? ??--?? 应力单位为kg ／cm 2 。 试确定外法线为n i （也即三个方向余弦都相等）的微分斜截面上的总应力n P 、正应力σn 及剪应力τ n 。 题—图 16
龋齿的预防措施及治疗方法
龋齿的预防措施及治疗方法 龋齿是医学术语，就是指牙齿腐烂或蛀牙。龋齿可以穿透起保护作用的牙釉质，直达更柔软、脆弱的齿质(牙齿的主体)，并进一步侵害柔软的牙髓和牙髓里敏感的神经纤维。蛀牙引起疼痛的原因目前尚不得而知，但有人认为可能是因为细菌引起发炎、牙根表面外露，以及齿质内小管内液体水平不均衡所致。 症状： 早期的龋齿可能没有什么症状。过一段时间，当腐烂到达牙釉质时，牙齿可能会对甜食或冷热敏感。 诊断： 不管是日常检查，还是因为牙痛去看医生，每次牙医都会检查病人是否患有龋齿。 预防措施： 只要减少口腔内的牙渍和细菌数量，就可以预防蛀牙。最好的方法是每天刷牙和用牙线剔牙，同时每年进行两次专业的牙齿清洁。平时少吃含糖或淀粉食物，也能减少口腔内的酸性物质。进食之后，口腔在数小时内都会维持在酸性状态，因此整天吃零食比两餐之间不吃零食更容易引起龋齿。 饭后咀嚼木糖醇口香糖有助于减少酸性物质。氟化物可以巩固牙齿。牙医会对患龋齿的风险进行评估，然后建议采用适当的氟化物治疗。对儿童来说，只要在臼齿完全长成后，让牙医在上面涂上一层牙科密封剂，就能对牙齿加以保护。 治疗方法： 龋齿的标准治疗方法是补牙。牙医先把蛀牙处的腐烂物质清除(通常需要麻醉镇痛)，然后对蛀牙进行填补。 填充物通常是由牙科用银粉制成，银粉是一种银灰色的物质，由银与铜或其它金属混合而成，可以增强硬度。银粉也可以用合成树脂制成，这样与牙齿的颜色相似，更为美观。银粉主要是用在臼齿和前臼齿上。树脂则主要用在门
牙上，当然所有的牙齿都可以使用。有需要时还可以使用金质填料，硬度更强， 1但更昂贵。如果蛀牙处的腐烂十分严重，余下的牙齿部分可能不足以支撑修复牙齿所需的大量填充物。这时牙医会把腐烂处去除，把受蛀部位补好，然后用人造牙冠包住牙齿。有时剩余的牙冠相对完整，反而是牙齿内部受损较为严重。在这种情况下，牙医可能建议向牙科专家求助，进行牙根管治疗。在这一过程中，牙髓医生会将牙髓除去，用惰性物质加以替代。多数情况下，需要用人造牙冠来替换天生的牙冠。 何时向专业人士求助： 牙齿腐烂初期通常不会感到疼痛。 早期的牙齿问题只由通过常规的专业检查和X光检查才能发现。如果发现自己的牙齿对冷热、甜食或者饮料敏感，请与牙科医生联系。 病情发展： 如果不对蛀牙进行诊断治疗的话，很可能会导致牙齿严重腐烂。最终，牙齿可能会因为受蛀未加控制而完全受损。 出现龋齿后，其它牙齿出现龋齿的风险也相应增加，原因有几个： ●不良的口腔卫生和饮食习惯不良，导致牙渍和酸性物质形成，引起最初的蛀牙，如果不加以纠正的话，还会导致更多牙齿被蛀。 ●细菌喜欢黏附在牙齿填充物和修复物上面，而不是平整的牙齿上，因为前者更容易出现新的龋孔。 ●填充物上的裂缝或缺口会令细菌和食物残渣进入牙齿内，导致填充物以下出现腐烂。 2
弹塑性力学试题答案完整版
弹塑性力学2008、2009级试题 一、简述题 1）弹性与塑性 弹性：物体在引起形变的外力被除去以后能恢复原形的这一性质。 塑性：物体在引起形变的外力被除去以后有部分变形不能恢复残留下来的这一性质。 2）应力和应力状态 应力：受力物体某一截面上一点处的内力集度。 应力状态：某点处的9个应力分量组成的新的二阶张量∑。 3）球张量和偏量（P25） 球张量：球形应力张量，即σ=0 00000m m m σσσ?????????? ，其中()13m x y z σσσσ=++ 偏量：偏斜应力张量，即x m xy xz ij yx y m yz zx zy z m S σστττσστττσσ?? -?? =-????-? ?，其中()13 m x y z σσσσ=++ 4）描述连续介质运动的拉格朗日法和欧拉法 拉格朗日描述也被称为物质描述，同一物质点在运动过程中的坐标值不变，物质体变形表现为坐标轴变形、基矢量的随体变化。 采用拉格朗日描述时，在变形过程中网格节点和积分点始终与物质点一致，便于精确描述材料特性、边界条件、应力和应变率； 欧拉描述也被称为空间描述。在欧拉描述中，当前构形被离散化，初始构形(参考构形)是未知的。由于采用了物质对固定网格的相对运动，它具有以下优点： 欧拉描述便于对固定空间区域特别是包含流动、大变形和物质混合问题的建模。 5）转动张量：表示刚体位移部分，即 1102211022110 22u v u w y x z x v u v w ij x y z y w u w v x z y z W ? ? ?? ??????--?? ? ? ??????? ???? ? ? ?????????? =-- ? ??? ? ??????????? ????????????-- ? ? ????????? ?? ?? 6）应变张量：表示纯变形部分，即
弹塑性力学习题及答案
1 本教材习题和参考答案及部分习题解答 第二章 2.1计算：(1)pi iq qj jk δδδδ，(2)pqi ijk jk e e A ，(3)ijp klp ki lj e e B B 。 答案 (1)pi iq qj jk pk δδδδδ=; 答案 (2)pqi ijk jk pq qp e e A A A =-; 解：(3)()ijp klp ki lj ik jl il jk ki lj ii jj ji ij e e B B B B B B B B δδδδ=-=-。 2.2证明：若ij ji a a =，则0ijk jk e a =。 （需证明） 2.3设a 、b 和c 是三个矢量，试证明： 2[,,]??????=???a a a b a c b a b b b c a b c c a c b c c 证：因为1 231 111232221 2 33 3 3i i i i i i i i i i i i i i i i i i a a a b a c b a b b b c c a c b c c a a a a b c b b b a b c c c c a b c ?? ???? ??????=?????????????????? ， 所以 1 231111232221 2 33 3 3 1 231 1112322212 333 3det det()i i i i i i i i i i i i i i i i i i a a a b a c a a a a b c b a b b b c b b b a b c c a c b c c c c c a b c a a a a b c b b b a b c c c c a b c ?? ??????????==??? ??????????????? 即得 123111 2 123222123333 [,,]i i i i i i i i i i i i i i i i i i a a a b a c a a a a b c b a b b b c b b b a b c c a c b c c c c c a b c ??????=???==a a a b a c b a b b b c a b c c a c b c c 。 2.4设a 、b 、c 和d 是四个矢量，证明： ()()()()()()???=??-??a b c d a c b d a d b c 证明：()()??=a b c d ?
弹塑性力学试题
弹塑性力学试题 (土木院15研) 考试时间：2小时 考试形式：笔试，开卷 一﹑是非题（下列各题，你认为正确的在括号内打“√”，错误的打“×”。每小题3 分，共21分） 1． 孔边应力集中的程度与孔的形状有关，圆孔应力集中程度最高。（ ） 2． 已知物体内P 点坐标P （x, y, z ）, P '点坐标P '（x+dx, y+dy, z+dz ）, 若P 点在x, y, z 方向的位移分别为u, v, w ，则P '点在x 方向的位移为dz z w dy y v dx x u u ??+??+??+ （ ） 3． 任何边界上都可应用圣维南（St. Venant ）原理，条件是静力等效。。 （ ） 4． 塑性力学假设卸载时服从初始弹性规律。（ ） 5． 弹性力学空间问题应变状态第二不变量为2 2 2 - yz xz xy z y z x y x γγγεεεεεε--++。（ ） 6． 弹性力学问题的两类基本解法为逆解法和半逆解法。（ ） 7． 全量理论中，加载时应力—应变存在一一对应的关系。（ ） 二﹑填空及简答题（填空每小题3分，共23分） 1． 弹性力学平面问题，结构特点是（ ），受力特点是（ ）。 2．求解塑性问题，可将应力——应变曲线理想化，分为5种简单模型，它们分别是（ ）。 2． 薄板小挠度弯曲中内力弯矩和剪力的量纲分别为（ ）、（ ）。 3． 比较Tresca 屈服准则和von Mises 屈服准则的相同点与不同点。（5分） 4． 弹性力学的几何方程是根据什么假设条件推导出来的?（4分） 6．简述弹性力学量纲分析的基本思路。（5分） 三﹑计算题（共56分） 1. 写出圆形薄板轴对称弯曲的弹性曲面方程。若受均布荷载0q 作用，推导（必须有推导过程）出其挠度w 的表达式。（8分） 2. 已知应力函数)(A 2 3 xy x +＝?，A 为常数。试求图中所示形状平板的面力（以表面法向和切向应力表示）并在图中标出。(8分)