원전 증기발생기 와전류검사 장치의 전기적 특성 측정

이희종,조찬희,유현주,문균영,이태훈,Lee, Hee-Jong,Cho, Chan-Hee,Yoo, Hyun-Joo,Moon, Gyoon-Young,Lee, Tae-Hun 한국비파괴검사학회 2013 한국비파괴검사학회지 Vol.30 No.3

원전 증기발생기는 원자로 냉각재 계통에서 발생한 열에너지를 터빈 계통의 주급수에 전달하여 터빈을 회전시키기 위한 증기를 생산하는 일종의 열교환기이다. 증기발생기 전열관의 손상은 증기발생기의 구조적 및 누설 건전성 유지 능력을 저해시키기 때문에 주기적으로 와전류검사를 수행하여 전열관의 건전성을 평가한다. 증기발생기 전열관의 건전성 평가는 보통 원자로 연료 재장전 기간 중에 수행된다. 현재 국내 증기발생기 전열관에 적용되는 와전류검사는 KEPIC 및 ASME 코드 요건에 따라 수행되며, 와전류검사 수행에 필요한 검사 시스템은 와전류검사 장치와 수집된 신호를 평가하기 위한 평가 프로그램으로 구성된다. 검사에 적용되는 와전류검사 시스템을 구성하는 핵심기기인 와전류검사 장치는 ASME 및 KEPIC 코드에서 총 고조파 왜곡율, 입출력 임피던스, 증폭기 직선성 및 안정성, 위상 직선성, 대역폭 및 복조필터 응답, 디지털 변환, 채널 간섭 등과 같은 전기적 특성을 측정하도록 규정하고 있다. 이에 따라 본 논문에서는 국내 최초로 개발한 원전 증기발생기 와전류검사 장치의 전기적 특성 측정을 위한 ASME 및 KEPIC 코드 요건을 설명하고, 이 요건에 따른 증기발생기 와전류검사 장치의 전기적 특성의 측정 결과를 제시하였다. A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

와전류검사 기술을 적용한 가압중수로 원전 압력관 비파괴검사

이희종,최성남,조찬희,유현주,문균영,Lee, Hee-Jong,Choi, Sung-Nam,Cho, Chan-Hee,Yoo, Hyun-Joo,Moon, Gyoon-Young 한국비파괴검사학회 2014 한국비파괴검사학회지 Vol.27 No.4

중수로 원자로는 한 개의 원자로용기로 구성된 경수로와는 달리 약 380여개의 연료채널(fuel channel)로 구성되어 있다. 연료채널을 구성하는 압력유지 기기인 압력관(pressure tube)은 지르코니움 합금(Zr-2.5wt% Nb) 재질로서 치수는 내경이 103.4 mm, 두께가 약 4.19 mm, 길이가 6.36 m인 튜브 형태의 관이다. 압력관은 내부에 핵연료 다발과 냉각재가 내장되며 압력관의 기능은 연료를 지지하고 열수송 유체인 중수($D_2O$)를 이송한다. 압력관의 단순한 기하학적인 형상으로 인하여 자동화 비파괴검사가 가능하고 접근성이 우수하다. 연료채널은 경수로형 원전과 동일하게 설치전과 운전중에 원자력안전위원회 법령 요건에 따라 주기적으로 엄격한 비파괴검사를 수행하여 건전성을 확인한다. 연료채널의 주기적 비파괴검사에는 초음파탐상 및 와전류탐상검사 기법을 적용한 체적 비파괴검사 기술이 적용된다. 이중에서 와전류탐상검사 기법은 초음파탐상검사에서 검출된 결함의 확인을 위한 보충검사기술로 적용되고 있지만 표면결함에 대한 검출능이 초음파탐상검사 기법보다 우수한 장점을 가지고 있다. 본 논문에서는 압력관 내부 표면 비파괴검사에 적용되고 있는 와전류탐상검사 기술의 압력관 내면에 발생할 수 있는 결함의 검출 및 깊이 측정 특성에 대한 연구결과를 기술하였다. 즉, 와전류검사 기술은 압력관 내면에 발생할 수 있는 아주 미세한 결함을 매우 우수한 분해능으로 검출할 수 있으므로 초음파탐상검사 결과 확인을 위한 보충기술로서 매우 유용하지만, 결함의 깊이 측정은 오차가 매우 크게 발생하므로 결함 깊이 측정에는 적합하지 않고 오직 표면결함 검출에만 적용하는 것이 바람직하다. A pressurized heavy water reactor (PHWR) core has 380 fuel channels contained and supported by a horizontal cylindrical vessel known as the calandria, whereas a pressurized water reactor (PWR) has only a single reactor vessel. The pressure tube, which is a pressure-retaining component, has a 103.4 mm inside diameter ${\times}$ 4.19 mm wall thickness, and is 6.36 m long, made of a zirconium alloy (Zr-2.5 wt% Nb). This provides support for the fuel while transporting the $D_2O$ heat-transfer fluid. The simple tubular geometry invites highly automated inspection, and good approach for all inspection. Similar to all nuclear heat-transfer pressure boundaries, the PHWR pressure tube requires a rigorous, periodic inspection to assess the reactor integrity in accordance with the Korea Nuclear Safety Committee law. Volumetric-based nondestructive evaluation (NDE) techniques utilizing ultrasonic and eddy current testing have been adopted for use in the periodic inspection of the fuel channel. The eddy current testing, as a supplemental NDE method to ultrasonic testing, is used to confirm the flaws primarily detected through ultrasonic testing, however, eddy current testing offers a significant advantage in that its ability to detect surface flaws is superior to that of ultrasonic testing. In this paper, effectiveness of flaw detection and the depth sizing capability by eddy current testing for the inside surface of a pressure tube, will be introduced. As a result of this examination, the ET technique is found to be useful only as a detection technique for defects because it can detect fine defects on the surface with high resolution. However, the ET technique is not recommended for use as a depth sizing method because it has a large degree of error for depth sizing.

초미세수술을 이용한 하지재건의 기술적 고찰

이희종,김성찬,김규남,윤치선,홍준표,Lee, Hee Jong,Kim, Sung Chan,Kim, Kyu Nam,Yoon, Chi Seon,Hong, Joon Pio 대한미세수술학회 2013 Archives of reconstructive microsurgery Vol.22 No.1

Purpose: The concept and development of perforator free flaps have led to significant advances in microsurgery. Ongoing developments in perforator free flap surgery are aimed at reducing complications and improving surgical outcomes. The aim of this study was to evaluate the effectiveness and application of supermicrosurgery in free flap surgery. Materials and Methods: A total of 267 patients with soft tissue defects of the lower extremity due to various etiologies from January, 2007 to January, 2013. The patients received either an anterolateral thigh free flap (n=83), a superficial circumflex iliac artery free flap (n=152), an upper medial thigh free flap (n=19), or a superior gluteal artery perforator free flap (n=13). Microanastomosis was performed using a perforator-to-perforator technique, either end-to-end or end-to-side. Results: The mean postoperative follow up period was eight months (range: one to 16 months) and flap loss occurred in 11 cases out of 267. All cases of flap loss occurred within two weeks of surgery due to either arterial insufficiency (n=5) or venous congestion (n=6). Conclusion: Supermicrosurgery enables the selection of the most efficient perforator for microanastomosis at the defect site. It also reduces the time required for dissection of recipient vessels, and reduces the possibility of injury to major vessels. Microsurgery using a vessel of less than 1 mm has been reported to increase the risk of flap failure; however, using the most advanced surgical tools and developing experience in the technique can produce success rates similar to those found in the literature.

2000년대 전반기 패션 컬렉션에 나타난 메이크업 특성에 관한 연구

이희종(Lee Hee Jong),구자명(Kuh Ja Myung) 한국인체미용예술학회 2006 한국인체미용예술학회지 Vol.7 No.1

  This study examines the trend of make-up with a focus on Paris, Milano, New York, and London Collections abroad and SFAA Collection and Seoul Collection at home from 2000 to 2005, and analytically compares the features found in the collections. For this, fashion-related magazines, books, theses, journals, and websites are utilized and photo materials the author worked on at domestic collections are included.<BR>  First, the trends include naturalism, ethnicism, reactionism, futurism, and deconstructionism, featuring as follows: Naturalism was found in bare nude, radiant, and tanning makeups; ethnicism was found in makeups applied with Chinese Jing Ju (京劇), ones applied with Japanese Geisha or Gabukki, Bollywood"s makeups from India, and primitive makeups from Africa; reactionism was found in black-white makeups in 1920-30s, hippie makeups in 1960s, glam rock makeups in 1970s, and glamor makeups in 1980s; futurism was found in cyber makeups, modern makeups, and surrealism makeups; and deconstructionism was found in humorous makeups and decadence makeups.<BR>  Second, the characteristics of make-up found in the fashion collections are compared as follows: Naturalism from overseas collections expresses mono-tone"s bare nude makeup featuring transparent and healthy image, while that from domestic collections expresses pastel-tone"s radiant makeup featuring romantic image. Ethnicism from overseas collections carries strong and experimental elements by applying mask, while that from domestic collections features simplicity by expressing black, white and red color on parts of the face. Reactionism from overseas featuresexpression to change past images, while that from domestic revives past images. Futurism from overseas expresses makeups with creative and queer design through surrealism, while that from domestic is characterized by achromatic and modern makeup, and such makeup with geometrical patterns. Deconstructionism from overseas expresses unsightly and mean image with the bold use of original colors and symbolic makeups from punk group, while that from domestic shows makeups featuring morbid atmosphere with white or black color.<BR>  On the whole, overseas collections feature boldness, creativeness, experimentalism, and informality, while domestic collections feature simple makeups that are mild without not too being magniloquent.

차체용 강판의 온도에 따른 동적 구성방정식에 관한 연구 (Ⅱ)

이희종(Hee-Jong Lee),송정한(Jung-Han Song),허훈(Hoon Huh),박성호(Sung-Ho Park) 대한기계학회 2007 大韓機械學會論文集A Vol.31 No.2

This paper is concerned with the empirical flow stress constitutive equation of steel sheets for an autobody with the variation of temperature and strain rate. In order to represent the strain rate and temperature dependent behavior of the flow stress at the intermediate strain rates accurately, an empirical hardening equation is suggested by modifying the well-known Khan?Huang?Liang model. The temperature and strain rate dependent sensitivity of the flow stress at the intermediate strain rate is considered in the hardening equation by coupling the strain, the strain rate and the temperature. The hardening equation suggested gives good correlation with experimental results at various intermediate strain rates and temperatures. In order to verify the effectiveness and accuracy of the suggested model quantitatively, the standard deviation of the fitted result from the experimental one is compared with those of the other two well-known empirical constitutive models such as the Johnson?Cook and the Khan?Huang?Liang models. The comparison demonstrates that the suggested model gives relatively well description of experimental results at various strain rates and temperatures.

교회 시설의 세금 부과에 관한 연구

이희종(Lee, Hee-Jong) 한양법학회 2016 漢陽法學 Vol.27 No.1

Since a long time ago, a church has been doing volunteering activity for a local community. Also a church has replaced the activity that should be done by the State while managing Haksagwan for college students, or opening the library, or a table-tennis room installed in a church to a local community residents. By the way, recently, the tax authorities have imposed taxes on the churches which are managing such facilities, increasingly causing inconvenience to church management. The tax law prescribes tax exemption benefits, such as property tax and acquisition tax, etc., to the facilities which are directly used for the relevant business by a church. Consequently, there has been a quarrel between a church and the tax authorities due to the different interpretation about the meaning of a church’s direct use of facilities for its unique business, i.e. for what a church is. There is no regulation specified in the law about what a church is for. Generally, the tax authorities and the court exclude the welfare work from tax exemption benefits while restricting the purpose of a church to worship and mission work. However, a church is not doing activity only for church congregation. A church is taking on an important role from the aspect relating to the relief of the poor, and social service. Accordingly, it’s natural that charitable work for a local community, or the activity for the relief of the disadvantaged people should be regarded as a part of the purposes of a church. It’s possible to confirm the word in the Bible ordering Christian believers to help and serve the poor neighbours of a local community everywhere in the Bible. Welfare work should be naturally acknowledged as the purpose of a church because it can be done by a church as a part of mission work. A church cannot exist without the social service caring for the socially underprivileged, and further, sharing and social service belong to the fundamental mission of a church. Also, it’s impossible to ignore the realistic necessity. Under the current circumstance where college students’ burden of housing expenses are rapidly increasing, along with the house-lease deposits and monthly rent skyrocketing across the nation, the church-managed Haksagwan could be a measure to improve college students’ residence requirement, and alleviate their burden of housing expenses. In short, a church is carrying out the function of providing housing service on behalf of the State, which fails to adequately provide it to college students, through the management of Haksagwan. If the tax authorities should impose legal controls like tax imposition, etc. on the church for Haksagwan management instead of including it in religious activity native to a church, it is feared that a variety of social welfare work developed by a church could be shrunk, let alone management of Haksagwan.

다중채널 와전류탐상검사 장치 개발(I)

이희종(Hee-Jong Lee),남민우(Min-Woo Nam),조찬희(Chan-Hee Cho),윤병식(Byung-Sik Yoon),조현준(Hyun-Joon Cho) 한국비파괴검사학회 2010 한국비파괴검사학회지 Vol.30 No.2

전자기유도(electromagnetic induction) 현상을 이용한 비파괴진단기법으로 최근까지 와전류탐상기법, 교류장측정기법, 자속누설검사기법, 그리고 원격장검사기법 등이 개발되어 활용되고 있었다. 이 기법중 와전류탐상기법은 오늘날 발전설비, 화학, 조선 및 군수설비 등의 열교환기 전열관 비파괴검사에 널리 적용되고 있다. 와전류탐상검사 시스템의 구성은 기능별로 와전류신호 합성 모듈, 아날로그 모듈, 디지털 신호처리를 위한 아날로그-디지털 변환 모듈, 전원공급장치 및 신호취득 평가 프로그램 등으로 구성되며, 본 연구에서는 다중채널방식의 와전류탐상검사 장치(하드웨어) 개발에 필요한 구성 요소중 1차적으로 와전류신호 합성 모듈, 아날로그 모듈을 설계 개발하였다. 본 연구에서 개발한 와전류탐상검사 장치의 특정은 주파수영역 및 시간영역 다중화 방식에 의한 최대 4개 주파수의 동시 적용이 가능한 다중채널장치이다. 와전류신호 합성 모듈, 아날로그 모듈을 구성하는 각 회로에서 와전류신호 발생, 변조, 전처리, 변조 및 신호 디스플레이를 위한 신호가 적절하게 처리되어 최종적으로 와전류신호 평가에 필수적인 리사쥬신호가 임피던스 평면 내에 디스플레이 되는 것을 확인하였다. Recently, the electromagnetic techniques of the eddy current testing(ECT), alternating current field testing, magnetic flux leakage testing and remote field testing have been used as a nondestructive evaluation method based on the electromagnetic induction. The eddy current testing is now widely accepted as a NDE method for the heat exchanger tube in the electric power industry, chemical, shipbuilding, and military. The ECT system mainly consists of the synthesizer module, analog module, analog-to-digital converter, power supplier, and data acquisition and analysis program. In this study, the synthesizer module and the analog module which are essential to the ECT system were primarily developed. The developed ECT system is basically a multifrequency type which is able to inject the maximum four frequencies based on the frequency and time domain multiplexing method. Conclusively, we confirmed that the EC signal was processed appropriately in each circuit modules, and the Lissajous EC signal was displayed in the impedance plane.

기업복지 서비스 유형이 조직몰입에 끼치는 영향

이희종(Hee-Jong Lee) 한국콘텐츠학회 2014 한국콘텐츠학회논문지 Vol.14 No.6

기업이 제공하는 각 종 복리후생 서비스들이 근로자들의 조직몰입에 영향을 끼치는 과정에서 중요한 역할을 하는 생활만족의 매개효과를 살펴 본 연구이다. 노동패널 11차년도 자료를 이용하여 분석한 결과 휴가, 가족지원, 미래대비 서비스가 모두 생활만족에 유의미한 영향을 끼치는 것으로 나타났다. 그러나 실제 제공 수준이 낮은 의료관련 지원은 생활만족에도, 조직몰입에도 유의미한 영향을 끼치지 못했다. 반면 미래대비 서비스의 경우 조직몰입에 직접적인 영향은 유의미하지 않고, 생활만족을 통한 효과만이 유의미한 것으로 나타나, 생활만족이 완전매개 역할을 하고 있는 것이 확인되었다. 결국, 기업이 제공하는 다양한 복리후생 서비스들은 근로자들의 일상 생활에 영향을 끼치는 서비스들로 복리후생 서비스가 조직몰입에 영향을 끼치는 과정에서 생활만족을 고려하는 것이 필요함을 보여 주었다. 앞으로의 복리후생연구에서 생활만족과의 관계에 더 많은 관심을 기울일 필요가 있음을 제언하였다. The purpose of this paper is to investigate how the employee benefits be related to the employees organizational commitments through life satisfaction. There are four types of employee benefits: holidays, family-friendly benefits, financial supports for future, and insurance supports for medical care. The results show that 3 types of benefits(holidays, family-friendly benefits, financial supports for future) are significantly associated with life satisfaction. Holidays and family-friendly benefits are positively related to employees organizational commitments, too. The findings further reveal that life satisfaction is full mediating factor between financial supports for future and organizational commitment. In case of holidays, family-friendly benefits, life satisfaction is partially mediated to organizational commitment. Findings are discussed in terms of the importance of life satisfaction through employee benefits.

임원배상책임보험에서의 고지의무와 화해금에 관한 연구

이희종(Lee Hee Jong) 한국보험법학회 2009 보험법연구 Vol.3 No.2

회사의 임원의 업무 수행은 주주, 종업원, 경쟁자, 감독기관 등 많은 곳으로부터 감시를 받고 있으며, 이들로부터 법적인 책임을 추궁당하는 경우도 많이 있다. 따라서 임원을 잠재적인 법적 책임으로부터 보호하는 수단을 제공하는 것이 필요해졌다. 임원배상책임보험이란 회사의 임원이 업무 수행과 관련하여 주주 또는 제3자로 부터 손해배상청구를 당하여 법적인 배상책임을 부담하는 경우에 그로 인하여 발생하는 임원의 손해를 보상하는 보험을 말한다. 이 보험은 1997년 외환위기 이후에 이용되기 시작하였는데 많은 문제점을 내포하고 있다. 이제 그 중에서 중요한 몇 가지 대한 문제에 대하여 논의하기로 한다. 첫째, 임원배상책임보험에서 청약서를 제출하고 질문표에 응답하는 자, 즉 고지의무를 이행하는 자는 피보험자인 임원이 아니라 회사의 대표이사이다. 따라서 대표이사가 고지의무를 위반한 경우에 이를 모르는 임원에 대해서도 보험자는 보험계약을 해지할 수 있는지가 문제된다. 현행 약관상으로는 대표이사가 보험자에 대한 고지의무를 위반한 경우에는 다른 피보험자인 임원도 임원배상책임보험에 의한 보호를 받을 수 없는 것이 원칙이다. 고지의무의 방식을 바꾸어서 대표이사가 보험 가입을 하되 대표이사가 고지할 사항을 제외하고는 피보험자인 당해 임원이 질문표에 대한 기재를 하도록 의무화하여 대표이사에 대한 고지의무 위반으로 다른 임원들이 보험에 의한 보호를 받지 못하는 문제점을 시정하여야 할 것이다. 둘째, 임원배상책임보험에 의해 보상되는 손해는 피보험자의 법률상 손해배상금과 소송비용으로 되어 있다. 임원배상책임보험에 의해 보상하는 법률상 손해배상금에 판결에 의한 손해배상금 이외에 화해금도 포함되는지가 명확하지가 않다. 앞으로 주주대표소송이 증가하게 되면 화해에 의하여 소송이 종료되는 경우도 늘어나게 될 것이고, 증권관련 집단소송에서도 화해가 이용될 가능성이 증대되고 있다. 따라서 화해금이 임원배상책임보험에 의해서 보상되는 손해의 범위에 포함되는지를 명확히 할 필요가 있다. 화해금의 성질을 대법원 판례와 같이 분쟁해결금으로 본다면 보험회사가 보상하는 손해의 범위에서 화해금을 제외할 이유가 없다고 본다. 그리고 임원배상책임보험의 화해금액의 결정에 대해서는 보험자의 동의가 필요하지 않다고 보는 것이 타당하다. The actions of directors and officers of all companies are subject to scrutiny from various parties such as shareholders, employees, competitors and regulators. And directors and officers shall be liable for the damages of the cor-poration. Therefore it is essential to provide with protection to directors and officers against such potential liabilities. Directors and Officers Liability Insurance is the insurance that compensates the loss from paying benefits for the company's board of directors who got a claim from the shareholders or third party for damages related to director's discharge of duty. This insurance has been used since financial Crisis occurred in 1997; however, it still contains many problems. From now, I will discuss for improving some critical issues among many problems. The person who discloses the material facts and signs the application in time of contracting of Directors and Officers Liability Insurance is not all the insureds but the CEO alone. If the CEO breaches the duty of disclosure to the insurance company, insured person, the board of directors, can not be protected under by Directors and Officers Liability Insurance in the current terms and conditions. In other words, it is irrational for the other innocent directors who do not know the fact of violated action made by CEO. The most appropriate way to prevent this kind of situation is to apply duty of disclosure individually with clear regulation. Directors and Officers Liability Insurance will pay damages and defense costs. It is not clear that the Directors and Officers Liability Insurance con-tains the settlements. While the loss explicitly includes the settlements, dam-ages, reconciliation, and defense costs in English clause, it does not in Korean clause. However, if the settlements has the same characteristic as a compensation for damages, distinctions will not be needed between com-pensation and composition. And it is appropriate that the decision of the settlement does not need the agreement of the insurer.

출생 체중 불일치를 보이는 쌍태임신의 주산기 예후

이희종(Hee Jong Lee),이준서(June Seo Lee),김행수(Haeng Soo Kim),양정인(Jeong In Yang),오준환(Jun Hwan Oh),한기수(Ki Su Han),오기석(Kie Suk Oh) 대한산부인과학회 2001 Obstetrics & Gynecology Science Vol.44 No.3

Objective : To evaluate the perinatal outcomes of twin pregnancies with birth weight discordancy and to determine factors affecting on the outcomes. Methods : We studied 367 pairs of twin delivered after 28 weeks of gestation at the Ajou University Hospital between June 1994 and June 2000. Twins were stratified into three groups according to the percent difference of birth weight. Birth weight difference less than 15%(concordant) was classified into control group(268 pairs), between 15% and 25% into group 1(72 pairs), and more than 25% into group 2(27 pairs). Perinatal outcomes of each group were assessed retrospectively. Results : In smaller twins, mean birth weight(control vs group 1 vs. group 2 : 2274.3±424.9 gm vs. 2012.9±303.2 gm vs. 1635.2±440.8 gm, p<0.05), duration of neonatal intensive care unit admission(7.6±11.5 days vs. 11.6±10.8 days vs. 18.6±14.4 days, p<0.05), and the frequency of neonatal jaundice(8.6% vs. 12.5% vs. 29.6%, p<0.05), the frequency of small for gestational age infant(8.2% vs. 40.3% vs. 74.1%, p<0.05), and perinatal mortality(2.6% vs. 2.8% vs. 11.1%, p<0.05) in group 2 showed statistically significant difference from control group. No difference was found in larger twins. In multiple logistic regression analysis, independent prognostic factors of discordant twin were gestational age and birth weight. Conclusion : In twin pregnancies with birth weight discordancy, larger twins showed no difference in perinatal outcomes but smaller twins with birth weight discordancy more than 25% showed significantly higher perinatal mortality and morbidity. However independent prognostic factor was not discordancy itself but gestational age and birth weight.